ASSIGNMENT QUESTION

YOUR COLLEGE IS HOSTING AN INTERNATIONAL EXPO ON TECHNICAL EDUCATION IN ZIMBABWEPREPARE A POWERPOINT PRESENTATION BASED ON UNDERPINNING OF FOUNDATIONSYOUR PRESENTATION SHOULD HAVE CLEAR amp INFORMATIVE ILLUSTRATIONS amp SHOULD FOLLOW THE FOLLOWING FORMAT

(a) DEFINITIONS

(b) REASONS FOR UNDERPINNING

(c) PROCEDURE USING THE

FOLLOWING MATERIALS

i CONCRETE

ii BEAMS

iii MINI PILES

UNDERPINNING

CHAKAMBA J

UNDERPINNING

OBJECTIVES

bull Define the term underpinning

bull Describe underpinningwhen it is needed and how it is done

bull State the reasons for underpinning

bull State the methods of underpinning a structure

UNDERPINNING OF BUILDINGS

INTRODUCTIONWhenever a new building is to be built especially

in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings

It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out

Only highly skillied and experienced personnel or companies should perform these operations

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING

CHAKAMBA J

UNDERPINNING

OBJECTIVES

bull Define the term underpinning

bull Describe underpinningwhen it is needed and how it is done

bull State the reasons for underpinning

bull State the methods of underpinning a structure

UNDERPINNING OF BUILDINGS

INTRODUCTIONWhenever a new building is to be built especially

in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings

It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out

Only highly skillied and experienced personnel or companies should perform these operations

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING

OBJECTIVES

bull Define the term underpinning

bull Describe underpinningwhen it is needed and how it is done

bull State the reasons for underpinning

bull State the methods of underpinning a structure

UNDERPINNING OF BUILDINGS

INTRODUCTIONWhenever a new building is to be built especially

in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings

It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out

Only highly skillied and experienced personnel or companies should perform these operations

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING OF BUILDINGS

INTRODUCTIONWhenever a new building is to be built especially

in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings

It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out

Only highly skillied and experienced personnel or companies should perform these operations

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

INTRODUCTIONWhenever a new building is to be built especially

in urban areasit is quite common to have the foundations lower than the foundations of adjacent buildings

It is therefore essential that the stability of the existing building(s) is safeguarded by performing underpinning as well as shoring`that care and forethought should be undertaken if these operations are to be successfully carried out

Only highly skillied and experienced personnel or companies should perform these operations

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

DEFINITIONSTECHNICAL EDUCATIONbull It is academic and vocational preparation of students for jobs

involving applied science and modern technology bull It is also understood to include the theoretical amp practical scientific

knowledge and skills that permit a person receiving such education to solve production engineering and economic problems in his speciality(encyclopedia2 the freedictionary)

UNDERPINNINGbull It is a broad term to describe the process of modifying

an existing foundation by adding supportbull It can also be described as the installation of temporary

or permanent support to an existing foundation to provide either additional depth or an increase in bearing capacity(Nemati 2007)

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

DEFINITIONS Cont

bull Underpinning can also be reffered to as a process of strengthening the foundation of an existing building or other structure(wikipediathe free encyclopedia)

REASONS FOR UNDERPINNING Construction of a new project with a deeper

foundation adjacent to an existing building

To enable the foundations to be deepened for structural reasons eg to construct a basement or addition of another storey to the building

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

REASONS contTo support a structure that is sinking or tilting due to

poor soil or instability of the superstructureChange in use of a structureAs a safeguard against possible settlement of a

structure when excavating close to or below its foundation level

To support a structure while making alteration to its foundations or main supporting members

To increase the width of a foundation to permit heavier loads to be carried eg when increasing the height of a building with new levels

To enable a building to be moved bodily to a new site

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

REASONS ContThe original foundation is simply not strong or

stable enough

The properties of the soil supporting the foundation may have changed possibly through subsidence or were mischaracterized during design stages

Settlement of an existing structure

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNED FOUNDATIONS

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

SOME CAUSES OF SETTLEMENT ON A BUILDING

Lowering of the water table due to tidal fluctuationswellsfor a water district etc

Lowering of the water table can then cause tops of timber piles to decay overtime and will require remedial underpinning

Rising of the water table in some soils can effect a decrease in bearing capacity of the soil causing settlement on the building which will then require underpinning

Construction of buildings on unsuitable bearing material or over compressible layer eg peatorganic silts or poorly compacted backfill may also cause settlement

Earthquakesfloods or other natural causes can cause the structure to move thereby requiring stabilisation of foundation soils or footings

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

DETERMINING THE NEED FOR UNDERPINNING

Underpinning as a direct support of an existing building foundation provides the opportunity to preload ie jacking to limit settlement and improve poor foundations

When a structure starts showing signs of settlement or distress it is of utmost importance to precisely monitor the settlement or movement by a professional on a dailyweekly or monthly basis

Data collected or readings will indicate if the movements are decreasing or increasing

Analyzing the results will also tell whether underpinning is required or not to safeguard the structure eg cracks or any other weaknesses

Before the beginning of any excavation on a new structure a professional must examine all the structures in close proximity to the construction site so as to determine whether underpinning is also necessaryNash 1988146

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

PROCEDURES INVOLVED WHEN USING PILES FOR UNDERPINNING

The piles are formed of precast concrete sections Each section has a steel-linked hole running through it The steel lining helps the locating of the sections and ensures

that they are all in line

THE PROCESS

A hole is dug below the existing foundation of the structure The first section which has a pointed steel toe-piece to make

penetration into the ground easier is placed into position below the foundation

A bearing plate is then positioned between the jack and the foundation

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

PROCESS contThe jack is then put between the first section and the

bearing plate and the first section is forced downward by the hydraulic jack powered by a pump outside the excavation

When the top of the first section is almost flush with the groundthe jack is removed and the process is repeated with the second and subsequent sections

As each section is addeda length of steel tube is inserted into the hole and grouted into position to make an effective joint between the sections

The operation is continued until the pressure gauge indicates sufficient penetration resistance to ensure adquate bearing capacity

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

THE PROCEDURES INVOLVED WHEN UNDERPINNING BUILDINGS cont

The wall to be underpinned must be carefully inspected for any cracks or weaknesses and these carefully noted

The wall should then be divided into a convenient number of working baysgenerally not exceeding about 15mdepending on the quality and stability of the wallThese working bays should have sufficient room to enable a person to work inside them

A batten should now be fixed along the face of the wall throughout its length to act as a datum

A sequence of working which will often be determined by the conditions on the site and the accessibility of the working area adjacent to the wall should now be carefully outlined

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

PROCEDURE contNo two adjacent bays must be excavated at the

same time If consecutive bays have to be worked init is essential that the first bay is fully completed and allowed to harden before work is begun on the second bay

Each bay excavated in turnusually by handTheearth is taken out at the front of the bay which allows support to be given to the foundations for as long as possiblewhile this excavation is being dug

The earth is then dug out from underneath the foundations until new level is reached

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

PROCEDURE contThe ground is now levelled and thoroughly rammed

The projection of the foundations is cut off so that it is flush with the face of the wall

The foundation concrete is laid to the required thicknessprovided there is adquate projection on both side of the wallAny water in the excavation should be pumped out first

The brickwork is then built up in the working bay with good quality bricks and cement mortar usually 13 or 14

The work should be thoroughly pinned up to the concrete

The gap behind the new wall can be filled in with hardcore or weak concrete as the new wall is builtNash 1988146

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING OF FOUNDATIONS

UNDERPINNED STRUCTURE CONVENTIONAL PIT METHOD

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING METHODSo The means and methods of supporting a

structure foundation depends on some of the following factors

Foundation Loads static and dynamicpermanent and temporary

Type and magnitude of allowable structural movement iedeformations

Subsurface soil conditions

Subsurface ground water conditions

Access and mobility to the foundations

Potential for environmental hazards

Seismic loading

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

WAYS OF ACHIEVING UNDERPINNING It can be done by

i Load transfer

ii Soil treatment or

iii A combination of the above two mechanisms

LOAD TRANSFER

This literally take structural loads and transfer them to an underlying stratum that is more suitable for support

SOIL TREATMENT

This changes the physical properties of the ground to make it stronger and more supportive often without any change to existing foundations

In some cases ground treatment can be utilized to strengthen the ground while also acting as a load transfer

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING METHODS There are numerous methods that can be used

when underpinning

Each methods having its own specific soil and loading conditions where its application is most effective

In some cases constructability can also determine the system to be used

Each method have also its own advantages and disadvantages depending on the specific characteristics of the project

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

1 CONVENTIONAL PIT METHOD

o It consists of enlarging and or deepening existing foundations by removing soil from beneath the foundations and replacing it with concretereinforcements and a grout material

o The structure can also be temporary shored to prevent settlementDISADVANTAGES OF THE PIT METHOD

i It often results in moderate deformation of the structureii Unsafe working conditions

ADVANTAGES OF THE PIT METHOD i Simplicity of the engineeringii Low cost of labour to produce the resultiii There is continuity of the structurersquos uses during construction

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

2 JET GROUTING

It is a load transferring system for the underpinningoftenalso serving as an excavation support and ground water control system

It is an in-situ method of construction undertaken beneath foundations

High velocity injection of fluidsoften enclosed in air erodes the soils and replaces the soil with and engineered groutforming a cementations product known as SOILCRETE that is capable of attaining unconfined compressive strengths in excess of 703 kgcm2

Groups of 1 to 12m diameter soilcrete columns are constructed to transfer foundation loads to underlying suitable bearing material

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

USE OF JET GROUTING METHODIT IS A LOAD TRANSFERRING SYSTEM FOR THE UNDERPINNING

SERVING AS AN EXCAVATION SUPPORT AND GROUND WATER CONTROL SYSTEM

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

ADVANTAGES OF JET GROUTINGi Work is accomplished safely above grade and

sequenced so that little or no structural deformation occurs

ii It is most widely used for underpinning historical and sensitive structures

iii Can also be used to construct deep foundationsinsite gravity wall structures and groundwater cut off structures

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

3MICROPILES It is used to stabilize or upgrade existing foundation by

installing micropiles through pre-drilled holes determined by load characteristics

Micropiles are described as small diameter piles that can be installed in almost any type of soil and that can carry loads up to 500 tonnes depending on the type of it

These micropiles are steel reinforced placed into a small diameter hole and scaled to the ground by grout injections under relatively high pressure

Micropiles are widely recognized as a common remedial option for underpinning structures having foundations problems after completion or during service period

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

ADVANTAGES OF MICROPILESi They have high carrying capacity

ii Less site constraint problems

iii Low noise and vibration

iv It is a self ndashsustained operation

v It can be designed to have very low settlement

DISADVANTAGES OF MICROPILES

i Higher cost as compared to other pilling systems

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

TYPES OF MICROPILES Pile and Beam

Pile and Cantilever Beam

Knuckle pile

Piled raft

Angle pile

Cantilever Ring Beam

Twin pile

Jack Down piles

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

METHODS OF UNDERPINNING

1NEEDLE BEAM 2NEEDLE WALL

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING METHODS

3CANTILEVER NEEDLE BEAM 4UNDERPINNING RAILWAY BRIDGE

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

UNDERPINNING METHODS

FOUNDATION UNDERPINNING FOUNDATION UNDERPINNING

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

CONCLUSIONbull Finally it is important to note that underpinning

works require experts in the design and execution levels

bull Because of its complexity and specially the dangerousness for the renovation building and the buildings around itsafe working practices should be undertaken

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd

REFERENCES

httpencyclopedia2thefreedictionarycom|Technical Education Accessed on 06012014

httpcourseswashingtoneduc|cm420underpinningpdfAccessed on 06012014

NashWG(1988)Brickwork 3 revised third editionEssexAnchor Press Ltd