program calcul geotehnic

8/11/2019 program calcul geotehnic

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0BChapter 1. Analysis settings and settings administrator

This chapter explains the correct use of Settings administrator that serves to choose standards,

partial factors and verification methodology. It is the basic step needed for all GEO5 programs.

Introduction

GEO5 software is used in 90 countries worldwide. Engineering tasks are the same everywhere

to prove that the construction is safe and well designed.

The basic characteristic of structures (eg. geometry of wall, terrain, localization of anchors

etc.) are the same all over the world; the way of proving that the construction is safe and the theory

of analysis used are different. Large quantities of new theories and mainly partial factors of analysis

lead to input of large amounts of data and complicated programs. The Settings administrator wascreated in GEO5 for version 15 to simplify this process.

In the Settings administrator are defined all input parameters, including standards, methods

and coefficients for the current country. The idea is that each user will understand the Settings defined

in the program (or will define a new Setting of analysis), which the user then uses in their work.

To the Settings administrator and Settings editor the user then goes only occasionally.

Assignment:

Perform an analysis of a gravity wall per the picture below for overturning and slip according to

these standards and procedures:

1)

CSN 73 0037

2) EN 1997 DA1

3) EN 1997 DA2

4) EN 1997 DA3

5)

Safety factor on SF=1.6


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Scheme of the gravity wall for analysis

Solution

Firstly, input the data about the construction and geological conditions in the frames:

Geometry, Assign and Soils. Skip the other frames because they are not important for this

example.

Frame Geometry input of dimensions of the gravity wall


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Table with the soil parameters

Soil

(Soil classification)

Unit weight

3mkN

Angle of

internal friction

[ ]ef

Cohesion

of soil

[ ]kPacef

Angle of friction

structure soil

[ ]=

MG Gravelly silt,

firm consistency19,0 30,0 0 15,0

In the frame Assign, the first soil will be assigned automatically to the layer or layers.

This can be changed when necessary.

When the basic input of construction is done, we can choose standards, and then finally run

the analysis of the gravity wall.

In the frame Settings click the button Select and choose number 8 Czech Republic

old standards CSN (73 1001, 73 1002, 73 0037).

Dialog window Settings list

Note: The look of this window depends on standards that are currently active in the Settings

administrator more information in the help of the program (press F1). If the setting you want to use

isn`t on the list in the dialog window Settings list, you can activate it in the Settings administrator.

Now, open up the frame Verification and after analyzing the example record the utilization

of construction (in the frame Verification) - 53,1% resp. 66,5%.


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Frame Verification results of the analysis using CSN 73 0037 standard

Then return to the frame Settings and choose number 3 Standard EN 1997 DA1.



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Again, open the frame Verification and record the result (55,6% and 74,7%)

for EN 1997, DA1.

Frame Verification results of analysis for EN 1997, DA1

Repeat this procedure for settings number 4 Standard EN 1997 DA2 and number 5

Standard EN 1997 DA3.

The analyzed utilization of constructions are (77,8% and 69,7%) for EN 1997, DA2 or (53,5%

and 74,7%) for EN 1997, DA3.


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Variant 5 (analysis using Safety factors) is not as simple. In the frame Settings click on

Edit. This will show you the current analysis settings. Change the verification methodology to

Safety factors (ASD) and then input safety factor for overturning and sliding resistance as 1.6.

Dialog window Edit current settings: Gravity wall

Press OK and run the analysis. (69,0% and 77,1%).

Frame Verification analysis results for SF = 1.6


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If you would like to use this setting more often, it is good to save this setting by clicking

on Add to administrator, rename is as shown below, and next time use it as a standard setting.

Dialog window Add current settings to the Administrator

Dialog window Settings list then looks like this:



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Verification

Utilization in percentage using each standard is:

Overturning Slip

1) CSN 73 0037 53,1 66,5

2)

EN 1997 DA1 55,6 74,7

3)

EN 1997 DA2 77,8 69,7

4) EN 1997 DA3 53,3 74,7

5)

Safety factor on SF=1.6 69,0 77,1

The analysis is satisfactory using the selected analysis standards.

Note: This simple method can be used to compare retaining structures or stability analyses. When

analyzing foundations, the load (basic input data) must be computed according to relevant standards.

That is the reason why it doesnt make sense, to compare foundation design by various standards

with the same values of load (nominal values).


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In the frame Geometry choose the wall shape and enter its dimensions.

Frame Geometry


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In the frame Material enter the material of the wall.

Frame Material Input of material characteristics of the structure

Then, define the parameters of soil by clicking Add in the frame Soils. Wall stem is normally

analyzed for pressure at rest. For pressure at rest analysis, select Cohesionless.

Dialog window Add new soils


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Note: The magnitude of active pressure depends also on the friction between the structure and soil. The friction

angle depends on the material of construction and the angle of internal soil friction normally entered in the

interval ) ef 3231


Soil


Profile

[ ]m

Unit weight

3mkN

Angle of

internal

friction

[ ]ef

Cohesion

of soil

[ ]kPacef

Angle of

friction

structure soil

[ ]=

S-F Sand with trace of

fines, medium dense soil0,0 4,0 17,5 28,0 0,0 18,5

MS Sandy silt, stiff

consistency, 8,0


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Frame Water

In the next frame define Surcharge. Here, select permanent and strip surcharge on the terrain acting as

a dead load.

Dialog window New surcharge

In the frame FF resistance select the terrain shape in front of the wall and then define other parameters

of resistance on the front face.


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Frame FF resistance

Note: In this case, we do not consider the resistance on the front face, so the results will be conservative. The

FF resistance depends on the quality of soil and allowable displacement of the structure. We can consider

pressure at rest for the original soil, or well compacted soil. It is possible to consider the passive pressure if

displacement of structure is allowed. (for more information, see HELP F1)

Then, in the frame Stage settings choose the type of design situation. In this case,

it will be permanent. Also choose the pressure acting on the wall. In our case, we will choose active pressure,

as the wall can move.

Frame Stage settings

Note: Wall stem is dimensioned always on earth pressure at rest, i.e., the wall cant be moved. The possibility of

evaluating the stem and the wall of the active pressure is considered only in exceptional cases - such as the

effects of the earthquake (seismic design situation with partial coefficient equals 1.0).

Now, open up the frame Verification, where you analyze the results of overturning and slip of the cantilever

wall.


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Frame Verification

Note: The button In detail in the right section of the screen opens a dialog window with detailed information

about the analysis results.

Analysis results:

The verification of slip is not satisfactory, utilization of structure is

Overturning: 52,8 % 97,10933,208 =>= klvzd MM [kNm/m] SATISFACTORY.

Slip: 124,6 % 94,8178,65 =


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Change of the design: change of the geometry of the wall

Return to the frame Geometry and change the shape of the cantilever wall. For increasing

the resistance against slip we introduce a base jump.

Frame Geometry (Changing dimensions of cantilever wall)

Note: A base jump is usually analyzed as an inclined footing bottom. If the influence of the base jump

is considered as front face resistance, then the program analyses it with a straight footing bottom, but FF

resistance of the construction is analyzed to the depth of the down part of the base jump (More info in HELP

F1)

Thenanalyze the newly designed construction for overturning and slip.


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Frame Verification

Now, the overturning and slip of the wall are both satisfactory.

Then, in the frame Bearing capacity, perform an analysis for design bearing capacity

of the foundation soil 175 kPa.

Frame Bearing capacity

Note: In this case, we analyze the bearing capacity of the foundation soil on an input value, which we can get

from geological survey, resp. from some standards. These values are normally highly conservative, so it is

generally better to analyze the bearing capacity of the foundation soil in the program Spread footing that takes

into account other influences like inclination of load, depth of foundation etc.


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Next, in the frame Dimensioning chose wall stem check. Design the main reinforcement into the stem

10pcs. 12 mm, which satisfies in point of bearing capacity and all design principles.

Frame Dimensioning

Then, open up the frame Stability and analyze the overall stability of the wall. In our case, we will use

the method Bishop, which result in conservative results. Perform the analysis with optimization of circular

slip surfaceand then leave the program by clicking OK. Results or pictures will be shown in the report of

analysis in the program Cantilever wall.


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Slope stability program

Conclusion/ Result of analysis bearing capacity:

Overturning: 49,5 % 16,10852,218 =>= klvzd MM [kNm/m] SATISFACTORY

Slip: 64,9 % 47,6427,99 =>= posvzd HH [kN/m] SATISFACTORY

Bearing capacity: 86,3 00,17506,151 =>= dR [kPa] SATISFACTORY

Wall stem check: 78,7 % 71,13392,169 =>= EdRd MM [kNm] SATISFACTORY

Overall stability: 40,8 % Method Bishop (optimization) SATISFACTORY

This cantilever wall is SATISFACTORY.


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Chapter 3. Verification of gravity wall

In this chapter an analysis of an existing gravity wall for permanent and accidental design situations is

performed. Construction stages are also explained.

Assignment

Using EN 1997-1 (EC 7-1, DA2) standard, analyze an existing gravity wall for stability, overturning,

and slip .

Road traffic acts on the wall with magnitude of 10 kPa. Check the possibility to install the barrier on

the top of the wall. An accidental load from a car crash is considered as 50 kN/m and it acts

horizontally at 1,0 m. Dimensions and shape of the concrete wall can be seen in the picture below.

Inclination of the terrain behind the construction is 10 , the foundation soil consists of silty sand.

The friction angle between the soil and wall is 18 .

Determination of bearing capacity and dimensioning of the wall is not part of this task. In this

analysis, consider effective parameters of soil.

Scheme of the gravity wall - assignment

Solution:

For analyzing this task, use the GEO5 program Gravity wall. In this text, we will describe

the steps of analyzing this example in two construction stages.

1

st

construction stageanalyzing the existing wall for road traffic. 2

ndconstruction stageanalyzing impact of vehicle to the barrier on the top of the wall.


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Basic input: Stage 1

In the frame Settings click on Select and choose Nr. 4 Standard EN 1997DA2.


Then, in the frame Geometry, select the shape of the gravity wall and define its parameters.

Frame Geometry


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In the next step, input the material of the wall and geological profile. Unit weight of wall is

324 mkN . Wall is made from concrete C 12/15 and steel B500. Then define parameters of soil

and assign them to the profile.


Soil


Unit weight

3mkN

Angle of

internal friction

ef

Cohesion

of soil

kPacef

Angle of friction

structuresoil

MSSandy silt,

firm consistency18,0 26,5 12,0 18,0


Note: The magnitude of active pressure depends also on friction between the structure and soil in the

angle ef 32

31 . In this case we consider the influence of friction between the structure

and soil with value of ef

3

2

( =18

), when analyzing earth pressure. (More info in HELPF1).


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In the frame Terrain select the shape of terrain behind the wall. Define its parameters, in

terms of embankment length and slope angle as shown below.

Frame Terrain

In the next frame, define Surcharge. Input the surcharge from road traffic as Strip, with

its location on terrain, and as a type of action select Variable.

Dialog window Edit surcharge


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In the frame FF resistance choose the shape of the terrain in front of the wall and define the

other parameters of front face resistance.

Frame Front face resistance

Note: In this case, we do not consider resistance on the front face, so the results will be conservative.

The FF resistance depends on the quality of soil and allowable displacement of the structure. We

consider pressure at rest for the original soil or well compacted soil. It is possible to consider passive

pressure only if displacement of structure is allowed. (More info in HELPF1).

In the frame Stage settings select the type of design situation. In the first construction stage,

consider the permanent design situation.



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Now open up the frame Verification, where we analyse the gravity wall for overturning

and slip.

Frame Verification stage 1

Note: The button In detail in the right section of the screen opens a dialog window with detailed

information about the results of the analysis.

Dialog window Verification (in detail)

Note: For analyses based on EN-1997, the program determins if the force acts favorably or

unfavorably. Next each force is multiplied by the corresponding partial factor which is them on the

report.


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Then, open up the frame Stability and analyze the overall stability of the wall. In our case,

we will use the method Bishop, which results in conservative results. Perform an analysis

with optimization of circular slip surface and then validate everything by clicking OK.

Results or pictures will be shown in the report of analysis in the program Gravity wall.

Program Slope stability stage 1

Analysis results: Stage 1

When analyzing bearing capacity, we are looking for values of overturning and slip of the wall

on the footing bottom. Then we need to know its overall stability. In our case, the utilization of the

wall is:

Overturning: 70,0 % 73,26391,376 klvzd MM [kNm/m] SATISFACTORY.

Slip: 90,6 % 17,13853,152 posvzd HH [kN/m] SATISFACTORY.

Overall stability: 72,3 % MethodBishop (optimization) SATISFACTORY.


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Basic input: Stage 2

Now, add construction stage 2 using tool bar in the upper left corner of the screen.

Toolbar Stage of construction

In this stage, define the load from the impact of the vehicle to the barrier, using the frame

Inputforces. The load ais accidental and considers the impact of a vehicle with a weight of 5 tons.

Dialog window Edit forceconstruction stage 2 (accidental design situation)

Then open the frame Stage settings change the design situation on accidental.


The data in the other frames that we entered in stage 1 has not changed , so we dont have toopen these frames again. Select the frame Verification to perform the verification on overturning

and slip again.


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Frame Verification stage 2

Analysis results: Stage 2

From the results, we see, that the existing wall is not satisfactory for impact of a vehicle

to the barrier. In this case, utilization of the wall is:

Overturning: 116,3 % 13,56862,488 klvzd MM [kNm/m] NOT OK.

Slip: 102,9 % 35,14239,138 posvzd HH [kN/m] NOT OK.

Conclusion

The existing gravity wall in case of bearing capacity satisfies only for the first construction

stage, where road traffic acts. For the second construction stage, which is represented as impact to the

barrier on the top of the wall by a vehicle of 5 tons, the wall is not satisfactory.

As a solution to increase bearing capacity for overturning and slip it is possible to introduce

soil anchors. alternatively it is possible to place a barrier on the edge of the road, so the wall is not

loaded by a force from the crashing car.


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Chapter 4. Design of non-anchored restraint retaining wall

In this chapter is the design of non-anchored retaining wall for permanent and accidental loads

(flooding).

Assignment

Design non-anchored retaining wall from pile sheeting using the EN 1997-1 (EC 7-1,

DA3) standard in non-homogenous geologic layers. The depth of excavation is 2,5 m.

The ground water table is at a depth of 1,0 m. Analyze the construction also for flooding; when

the water is 1,0 m above the top of the wall (mobile anti-flood barriers should be installed).

Scheme of non-anchored wall from pile sheeting assignment

Solution:

For solving this problem, we will use the GEO5 program, Sheeting design. In this text,

we will explain each step to solve this example:

1stconstruction stage: permanent design situation

2ndconstruction stage: accidental design situation

Design of geometry of the pile sheeting

Analysis result (conclusion).


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Basic input: Construction stage 1

In the frame Settings click on Select and then choose Nr. 5 Standard EN 1997

DA3.


Then, input the geological profile, parameters of soil and assign them to the profile.



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Soil


Profile

[ ]m

Unit weight

3

mkN

Angle of

internal

friction

[ ]ef

Cohesion

of soil

[ ]kPacef

Angle of friction

structure soil

[ ]=

S-F Sand with trace

of fines, medium

dense soil

0,0 1,5 17,5 29,5 0,0 14,0

SC Clayey sand,

medium dense soil1,5 2,5 18,5 27,0 8,0 14,0

CL, CI Clay with

low or mediumplasticity,

firm consistency

from 2,5 21,0 19,0 12,0 14,0

In the frame Geometry, select the shape of bottom of the excavation and input

its depth.

Frame Geometry

Note: coefficient of reduction of earth pressure below the ditch is considered while analyzing

braced sheeting (retaining wall with soldier beams) only; for a standard sheeting pile wall it

equals 1,0 For more information, see HELP (F1).

In this case, we do not use the frames Anchors, Props, Supports, Pressure

determination, Surcharge and Applied forces. The frame Earthquake also has no

influence for this analysis, because the construction is not located in seismic-active area.

In the frame Terrain, it remains horizontal.


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In the frame Water input the GWT value 1,0 m.

Frame Water 1stconstruction stage

Then, in the frame Stage settings, select the design situation as permanent.


Now, open up the frame Analysis and click on the button Analyze. This will

perform the analysis of the retaining wall.

Frame Analysis

Note: For cohesive soils is recommended by many standards to use minimal dimensioning

pressure acting on the retaining wall. The standard value for the coefficient of minimal

dimensioning pressure is Ka = 0,2. It means that minimum pressure on the structure is 0,2

of geostatic stress never less.


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Within the design of pile sheeting retaining wall, we are interested in the depth

of construction in the soil and internal forces on the structure. For the 1st construction stage,

the results of analysis are:

Length of structure: m83,4

Needed depth in the soil: m33,2

Maximum bending moment: mkNmM 21,28max,1 =

Maximum shear force: mkNQ 98,56max,1 =

In the next stage, we are going to show you how to analyse the minimum depth in soil

and internal forces in the soil for the accidental design situation floods.

Basic input Construction stage 2

Now, select stage 2 on the toolbar Stage of construction on the upper left corner

of your screen. (If needed, add a new one)

Toolbar: Stage of construction

In the frame Water, change the GWT behind the structure to a value -1,0 m. We will

not consider water in front of the structure.


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Frame Water

Then, in the frame Stage settings, select the design situation Accidental.


All other values are the same as in the 1stconstruction stage, so we dont have to change

data in other frames, so we go on to the frame Analysis and click again on the button

Analyze.

Frame Analysis


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In the 2ndconstruction stagethe analysis results are:

Length of structure: m56,6

Needed depth in the soil: m06,4

Maximum bending moment: mkNmM 00,142max,2 =

Maximum shear force: mkNQ 17,185max,2 =

Using the maximum bending moment, we will design pile sheeting.

The minimum length of pile sheeting is set as the maximum of necessary length

from construction stage 1 and construction stage 2.

Design of pile sheeting:

We design the pile sheeting based on the maximum bending moment using the table of pile

sheeting with allowable bearing capacities shown below.

Design of pile sheeting according to CSN EN 10 248-1 standards.

Based on the chart, we will select the pile sheeting VL 503 (500 340 9,7 mm) ,

the steel grade S 270 GP, of which the maximum bending moment is mkNM 0,224max = .

Safe design of structure is verified by equation:

mkNmMmkNMdov 142224 max =>=


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Analysis result:

In the design of non-anchored restraint retaining wall, we are verifying values

of minimum depth of the structure in the soil, and the internal forces in the structure:

Minimum depth of the structure in first stage: 2,33 m

Minimum depth of the structure in second stage: 4,06 m

So, we will design a pile sheeting with depth in the soil of 4,1 m and overall length

of 6,6 meters.

Conclusion:

The designed pile sheeting retaining wall VL 503 from S 270 steel with length of 6,6 meterssatisfies.


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Chapter 5. Design of anchored retaining wall

In this chapter, we will show you how to design a retaining wall with one row of anchors.

Assignment:

Design a retaining wall with one anchor row made from pile sheeting using EN 1997-1

(EC 7-1, DA3) standard. The depth of ditch is 5,0 m. The anchor row is 1,5 m below

the surface. The soils, geological profile, ground water table and shape of terrain are the same as

in the last task. Remove construction stage two so as to not consider flooding.

Scheme of the anchored wall from pile sheeting assignment

Solution:

For solving this problem, we will use a GEO5 program, Sheeting design. In this text,

we will explain each step of this example:

Analysis 1: permanent design situation - wall fixed at heel

Analysis 2: permanent design situation - wall hinged at heel

Analysis result (conclusion)


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Basic input: Analysis 1

Leave the frames Settings, Profile, Soils, Terrain, Water and Stage settings

from the previous problem without changes. Also, delete construction stage 2 if you are reusing

the file from problem 4.

In the frame Geometry, input the depth of the ditch as 5,0 m.

Open up the frame Anchors and click on the button Add. For this case, add one

anchor row in the depth of 1,5 m below the top of the wall with anchor spacing at 2,5 m.

Also define the length of the anchors (which has no effect in the Sheeting design program,

it is only for visualization) and slope of the anchors (15 degrees).

In frame Stage Settings choose permanent.

Frame Anchors

In the frame Analysis select support at heel. For now, select Wall fixed at heel.

Now perform the analysis.

Frame Analysis Stage of construction 1 (Wall fixed at heel)


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In our case, we need to know the sheet pile embedment depth and also the anchor force. For the

wall fixed at heel, the values are:

Length of construction: m72,10

Depth in soil: m72,5

Anchor force: kN77,165

Maximum moment: mkNm /16,89

Maximum shear force: mkN/27,128

Now, perform an analysis for wall hinged at heel (construction stage 2). Then, compare

the results and, depending on comparison, design the embedment depth.

Basic input: Analysis 2

Now, add a new verification in the upper left corner of the frame.

Toolbar: Verification

Select the option Wall hinged at heel and perform the analysis.

Frame Analysis Stage of construction 2 (Wall hinged at heel)


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For the wall hinged at heel, the values are:

Length of construction: m85,7

Depth in soil: m85,2

Anchor force: kN68,201

Maximum moment: mkNm /35,119

Maximum shear force: mkN/84,69

The results of analysis

The overall length of the structure should be in the interval of Hfixed Hhinged.

For wall fixed at heel is the length of the structure is longer, but the anchor force is smaller.

For wall hinged at heel, it is the opposite, so larger anchor force and shorter length

of the construction. It is the users task to design the dimensions of the structure.

Conclusion

In our design, we will use pile sheeting VL 503 from steel S 270 with an overall length

of 9,0 m, anchors with size of force 240 kN with anchor spacing of 2,5 m. In the next chapter,

we will check this structure in the program Sheeting check.

Note: The design cannot be taken as the final and it needs to be checked in the Sheeting check

program, because on the real structure there is redistribution of earth pressure

due to anchoring.


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Chapter 6. Verification of retaining wall with one anchor row

In this chapter, we will show you how to verify a designed retaining wall with verification of inner stability

of the anchors and overall stability of the structure.

Assignment

Verify the retaining wall that you designed in task 5.

Solution:

For solving this problem, we will use the GEO5 program, Sheeting check. In this text,

we will explain each step to solve this task:

Construction stage 1: excavation of ditch to a depth of 2,0 m + geometry of the wall

Construction stage 2: anchoring of the wall + excavation of ditch to a depth of 5,0 m.


To make our work easier, we can copy the data from the last task, when we designed the wall

in the Sheeting design program by clicking in this program on Edit on the upper toolbar and selecting

Copy data. In Sheeting check program click on Edit and then Paste data. Now we have most

of the important data from the last task copied in to this program, so we dont have to input much

of the needed data.

Dialog window Insert data


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In the frame Settings, select again the number 5 Standard EN 1997, DA3. Select the

analysis of depending pressures as Reduce according to analysis settings. Leave the coefficient

for minimum dimensioning pressure as 0,20.

Frame Settings (Analysis of pressures)

Note: the selection Analysis of depending pressures do not reduce allows the analysis of limit

pressures (active and passive) without the reduction of input parameters by partial factors. This is better

for estimation of real behavior of construction. On the other hand, it does not follow EN 1997-1 Standard.

(More info in HELP F1)

Then, open up the frame Modulus hk , and choose the selection analyze Schmitt.

This method for the determination of modulus of subsoil reaction depends on the oedometric modulus and

stiffness of the structure. (More info in HELP F1)

Frame Modulus hk

Note: the modulus of subsoil reaction is an important input when analyzing a structure by the method

of dependent pressures (elasto-plastic nonlinear model). The modulus hk affects the deformation, which is

needed to reach active or passive pressures. (More info in HELP F1)

In the frame Soils enter the following values for each soil type. Poissons ratio and the oedometric

modulus were not entered in the previous program, so they must be entered here.


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Soil Type


Poissons ratio

[ ]

Oedometric Modulus

[ ]MPaEoed

SF - Sand with trace of fines,

medium dense0,30 21,0

SC - Clayey sand, medium dense 0,35 12,5

CL - Clay with low or medium

plasticity, firm consistency0,40 9,5

In the frame Geometry define the parameters of the sheet pile type of wall, section length,

coefficient of pressure reduction below ditch bottom, geometry and material of the construction. From the

sheet pile database, select the VL 503 (500 340 9,7 mm).

Dialog window Edit section

Now, in the frame Excavation define the first ditch depth 2,50 m for the first

construction stage.


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Frame Excavation Stage of construction 1

Now, go to frame Analysis. In the left part of the frame, you can see the modulus of subsoil

reaction, in the right section earth pressures and displacement. (For more information, see HELP F1)

Frame Analysis Stage of construction 1


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Add another construction stage as indicated below. Here we define the anchoring of the wall and

overall excavation. We cannot change the frames Settings, Profile, Modulus Kh, Soils

and Geometry, because these data are the same for all construction stages. We will only change datain the frames Excavation and Anchors.

In the frame Excavation, change the depth of the ditch to the final depth 5,0 m.

Frame Excavation Stage of construction 2

Then, go to the frame Anchors and click on the button Add. For this structure, we will add

a row of anchors to a depth 1,5 m below the top of the wall (below the surface). Also define other

important parameters: overall length of the Anchor input as 10 m, slope angle as 15 and anchor spacing as

2,5 m. Enter a pre-stress force equal to 240 kN and the diameter of the anchor.

Frame Anchors Stage of construction 2


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Frame Analysis construction stage 2 (Deformation and pressure on the structure)

Verification of material and cross section:

Maximum moment behind the construction is 116,03 kN/m

Sheet pile VL 503 (500 340 9,7 mm), quality of steel S 270 GP satisfies.

(Allowable moment = mkNmMmkNMu 0,1160,224 max =>= )

Maximum displacement of structure 30,1 mm is also satisfactory.


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Verification of anchor stability

Now, open the frame Internal stability. You can see, that the internal stability of anchors

is not satisfactory. This means, that the anchor could tear from the soil.

Frame Internal stability not satisfactory result (anchor length 7,0 m, k = 0,2)

The reason for this is that the anchor is too short, so in the frame Anchors, change its length

to 9,0 meters. This newly designed anchor then satisfies the internal stability requirements.

Frame Internal stability satisfactory result (anchor length 9,0 m, k = 0,2)


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The last needed check is overall stability of the structure. Click on the button External stability.

This will open the Slope stability program. In the frame Analysis click on Analyze. We can now see,

that the slope stability is acceptable. For external stability we consider length of anchor 7,0 m.

Frame External stability

Analysis results - conclusion:

Analysis done:

Bearing capacity of cross section:

51.8 % mkNmMmkNMu 0,1160,224 max =>= SATISFACTORY.

Internal stability: 81,0 % kNFkNFvzd 24024,296 =>= SATISFACTORY.

Overall stability: 84.8 % Method Bishop (optimization) SATISFACTORY.

In this case, the designed construction satisfies in all checked parameters.


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Chapter 7. Verification of multi-anchored wall

In this chapter, we are showing how to design and verify a multi-anchored wall.

Assignment

Verify a multi-anchored wall made from steel soldier piles I 400 with a length

of 21,0 m. Depth of the ditch is 15,0 m. The terrain is horizontal. The surcharge acts

at the surface and is permanent with size of 20,25 mkN . The GWT behind

the construction is 10,0 m below the surface.

Scheme of the wall anchored in multiple layers

Table with the soil and rock parameters

Soil, rock(classification)

Profile[ ]m

Unit

Weight3mkN

Angle of

internalfriction

[ ]ef

Cohesion

of soil

[ ]kPacef

Deformation

modulus

[ ]MPaEdef

Poissons

Ratio[ ]

CL, CI Clay

with low or

medium

plasticity,

firm consistency

0,0 2,0 19,5 20 16 6,0 0,4

CS Sandy

clay,

firm consistency

2,0 4,5 19,5 22 14 7,0 0,35

R4 (good rock), 4,5 12,0 21 27,5 30 40,0 0,3


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low strength

R3 (good rock),

medium

strength

12,0

16,622 40 100 50,0 0,25

R5 (poor rock),

very lowstrength

16,6 17,4

19 24 20 40,0 0,3

R5 (poor rock),

very low

strength

17,4

25,021 30 35 55,0 0,25

R5 (poor rock),

very low

strength

from 25,0 21 40 100 400,0 0,2

Angle of friction between structure and soil is = 5,7 for all layers.

Also, the saturated Unit weight equals the Unit Weight above. Note that the Modulus

of deformation is being used for soil materials.

Table with position and geometry of the anchors

Anchor

no.

Depth

[ ]mz Length

[ ]ml Root

[ ]mlk Slope

[ ] Spacing

[ ]mb Anchor force

[ ]kNF

1 2,5 19,0 0,01 15,0 4,0 300,0

2 5,5 16,5 0,01 17,5 4,0 350,03 8,5 13,0 0,01 20,0 4,0 400,0

4 11,0 10,0 0,01 22,5 4,0 400,0

5 13,0 8,0 0,01 25,0 4,0 400,0

All anchors have a diameter mmd 0,32= , modulus of elasticity

GPaE 0,210= . Anchor spacing is mb 0,4= .

Solution

For solving this task, use the GEO5 program Sheeting Check. The analysis

will be performed in the classical way without reduction of input data so the real

behavior of the structure will be grasped. Internal stability of the anchor system

and overall stability will be checked with a safety factor of 1,5. This solution assumes

you have entered the soil types and profiles, and permanent load as listed above.


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In the frame Settings select option no. 1 Standard safety factors.

Then, go to frame Geometry and input the basic dimensions of the section, and also

the coefficient of pressure reduction below the ditch bottom, which is in this case 0,4.

Dialog window New section

Note. The coefficient of reduction of earth pressures below the excavation reduces

the pressures in the soil. For classical retaining walls this is equal 1,0. For braced

sheeting it is less than or equal to one. It depends on size and spacing of braces

(More info in help F1).

Now, we will describe the building of the wall stage by stage. It is necessary

to model the task in stages, to reflect how it will be constructed in reality. In each stage

it is necessary to look at values of internal forces and deformation. If the braced

sheeting is not stable in some stage of construction or if the analyzed deformation is too

large, then we need to change structure for example to make the wall embedment

longer, make the ditch shallower, increase the anchor forces etc.


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In construction stage 1, the ditch is made to depth of 3,0 m. In the stage 2,

anchor is placed at a depth of 2,5 m. The GWT behind the structure is at a depth

of 10,0 m beneath the surface.

Frame Anchors Construction stage 2

In the 3rdconstruction stage, the ditch is excavated to a depth of 6,5 m. In the 4 th

stage, anchor is placed at a depth of 5,5 m. The GWT is not changed so far.



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In the 5thconstruction stage, the ditch is excavated to a depth of 9,0 m. In the 6 th

stage, anchor is placed at the depth of 8,5 m. The depth of GWT is not changed.


In 7th construction stage, the ditch is excavated to a depth of 11,5 m.

In 8th

construction stage, an anchor is placed at the depth of 11,0 m. The GWT in frontof the wall is now at a depth of 12,0 m below the surface. The GWT behind

the structure is not changed.



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Note: Due to deformation of the structure the forces in anchors are changing.

These changes depend on the stiffness of the anchors and the deformation

of the anchors head. The force can decrease (due to loss of pre-stress force)

or increase. The forces can be pre-stressed in any stage of construction again

to the required force.

Results of analysis

On the pictures below are the analysis results of the last, 11thconstruction stage.

Frame Analysis (Kh + pressures) Stage of construction 11

Frame Analysis (Internal forces) Stage of construction 11


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Frame Analysis (Deformation + stresses) Stage of construction 11

All the stages are satisfactorily analyzed that means that the structure is stable

and functional in all stages of the construction. The deformation must also be checked

that it is not too large, as well as that the anchor force does not exceed the bearing

capacity of the anchor (The user must check this as this is not checked by the program

Sheeting check).

Maximum displacement of the wall is 28,8 mm, which is satisfactory.

Note: If the program does not find a solution in some of the construction stages,

then the data must be revised e.g. to make the structure longer, make the forces

in anchors larger, change the number or position of anchors, etc.


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Verification of cross-section of the structure

Open the frame Envelopes in the 1st construction stage, where you see

the maximum and minimum values of variables.

Maximum shear force: mkN24,237

Maximum bending moment: mkNm80,220

Frame Envelopes

The bending moment is calculated per one meter (foot) of structure, so we have

to calculate the moment acting on the soldier beam. The spacing of soldier beams

in our example is 2,0 m, so the resulting moment is 220,80 * 2,0 = 441,6 KNm.

Users can perform the verification of cross-section I 400 manually or using

another program such as FIN EC STEEL.

Verification (cross-sections I 400) output from FIN EC STEEL program


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Overall utilization of cross-section: %8,72

Verification of bearing capacity: kNmMkNmM Ry 6,441582,606 max, ==

This designed cross-section satisfies analysis criteria.

Note: Dimensioning and verification of concrete and steel walls is not part

of the program Sheeting Check, but is planned for a future version.

Analysis of internal stability

Go to the frame Internal stability in the last construction stage and look at maximum

allowable force in each anchor and the specified safety factor. The minimum safety

factor is 1.5.

Frame Internal stability

Note : The verification is done this way. At first we iterate the force in the anchor,

resulting in equilibrium of all forces acting on the earth wedge. This earth wedge

is bordered by construction, terrain, the middle of the roots of anchors

and the theoretical heel of structure. If an anchor is not satisfactory the best way

to resolve the issue is to make it longer or decrease the pre-stressed force.


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Verification of external stability

The last required analysis is external stability. The button will automatically

open the program Slope stability, where you perform overall stability analysis.

Program Slope stability

Conclusion

The structure was successfully designed with a maximum deformation

of 28,8 mm. This is satisfactory for this type of construction. Additionally, the limits

of forces in anchors were not exceeded.

Verification of bearing capacity of cross-section SATISFACTORY

Internal stability SATISFACTORY

Anchor nr. 4 (analyzed safety factor): 50,1>31,5 amin == SFSF .

External stability SATISFACORY

Safety factors (Bishop optimization): 50,1>92,2 == sSFSF .

The designed sheeting satisfies evaluation criteria.


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Chapter 8. Analysis of slope stability

In this chapter, we are going to show you how to verify the slope stabilityfor critical

circular and polygonal slip surfaces (using its optimization), and the differences between

methods of analysis of slope stability.

Assignment

Perform a slope stability analysis for a designed slope with a gravity wall. This is a

permanent design situation. The required safety factor is SF = 1,50. There is no water in the

slope.

Scheme of the assignment

Solution

For solving this problem, we will use the GEO5 program, Slope stability. In this text,

we will explain each step to solve this problem:

Analysis nr. 1: optimization of circular slip surface (Bishop)

Analysis nr. 2: verification of slope stability for all methods

Analysis nr. 3: optimization of polygonal slip surface (Spencer)

Analysis result (conclusion)


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Basic input Analysis 1:

In the frame Settings click on Select and choose option nr. 1 Standard safety

factors.


Then model the interface layers, resp. terrain using these coordinates:

Adding interface points


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Firstly, in the frame Interface input the coordinate range of the assignment. Depth of

deepest interface point is only for visualization of the example it has no influence on the

analysis.

Then, input the geological profile, define the parameters of soil, and assign them to the

profile.



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Note: In this analysis, we are verifying the long-term slope stability. Therefore we are solving

this task with effective parameters of slip strength of soils (efef c, ). Foliation of soilsworse

or different parameters of soil in one direction - are not considered in the assigned soils.


Soil


Unit weight3

mkN

Angle of internal

friction ef Cohesion of soil

kPacef Assigned Soil

Region

MGGravelly silt,firm consistency

19,0 29,0 8,01

S-FSand with traceof fines, dense soil

17,5 31,5 0,03

MSSandy silt, stiff

consistency, 8,0

rS

18,0 26,5 16,04

Model the gravity wall as a Rigid Body with a unit weight of3

0,23 mkN . The

slip surface does not pass through this object because it is an area with large strength. (More

info in HELPF1)

In the next step, define a surcharge, which we consider as permanent and strip with its

location on the terrain surface.

Dialog window New surcharges


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Note: A surcharge is entered on 1 m of width of the slope. The only exception is concentrated

surcharge, where the program calculates the effect of the load to the analyzed profile. For

more information, see HELP (F1).

Skip the frames Embankment, Earth cut, Anchors, Reinforcements andWater. The frame Earthquake has no influence on this analysis, because the slope is not

located in seismically active area.

Then, in the frame Stage settings, select the design situation. In this case, we

consider it as Permanent design situation.


Analysis 1circular slip surface

Now open up the frame Analysis, where the user enters the initial slip surface using

coordinates of the center ( x, y )and its radius or using the mouse directly on the desktopby

clicking on the interface to enter three points through which the slip surface passes.

Note: In cohesive soils rotational slip surfaces occur most often. These are modeled using

circular slip surfaces. This surface is used to find critical areas of an analyzed slope. For

non-cohesive soils, an analysis using an polygonal slip surface should be also performed for

slope stability verification (see HELPF1).

Now, select Bishopas the analysis method, and then set type of analysis as

Optimization. Thenperform the actual verification by clicking on Analyze.


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Frame Analysis Bishopoptimization of circular slip surface

Note: optimization consists in finding the circular slip surface with the smallest stabilitythe

critical slip surface. The optimization of circular slip surfaces in the program Slope stability

evaluates the entire slope, and is very reliable. For different initial slip surfaces, we get the

same result for a critical slip surface

The level of stability defined for critical slip surface when using the Bishopevaluation

method is satisfactory :

50,182,1 sSFSF SATISFACTORY.

Analysis 2:

Now select another analysis on the toolbar in upper right corner of your Analysis

frame in GEO5.

Toolbar Analysis

In the frame Analysis, change the analysis type to Standard and as method select

All methods. Then click on Analyze.


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Frame Analysis All methodsstandard type of analysis

Note: Using this procedure, the slip surface made for all methods corresponds to critical slip

surface from the previous analysis scenario using the Bishop method. For better results the

user should choose the method and then perform an optimization of slip surfaces.

The values of the level of slope stability are:

Bishop: 50,182,1 sSFSF SATISFACTORY.

Fellenius / Petterson: 50,161,1 sSFSF SATISFACTORY.

Spencer: 50,179,1 sSFSF SATISFACTORY.

Janbu: 50,180,1 sSFSF SATISFACTORY.

Morgenstern-Price: 50,180,1 sSFSF SATISFACTORY.

achuanc: 50,163,1 sSFSF SATISFACTORY.

Note: the selection of method of analysis depends on experience of the user. The most popular

methods are the method of slices, from which the most used is the Bishop method. The Bishop

method does yield conservative results.

For reinforced or anchored slopes other rigorous methods (Janbu, Spencer and Morgenstern-

Price) are preferable. These more rigourous methods meet all conditions of balance, and they

better describe real slope behaviour.

It is not needed (or correct) to analyze a slope with all methods of analysis. For example, the

Swedish method FelleniusPetterson yields very conservative results, so the safety factors

could be unrealistically low in the result. Because this method is famous and in some

countries required for slope stability analysis, it is a part of GEO5 software.


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Analysis 3polygonal slip surface

In the last step of analysis, input the polygonal slip surface. As a method of analysis,

select Spencer, as analysis type select optimization, enter a polygonal slip surface and

perform the analysis.

Frame Analysis Spenceroptimization of polygonal slip surface

The values of the level of slope stability are:

50,158,1 sSFSF SATISFACTORY.

Note: Optimization of a polygonal slip surface is gradual and depends on the location of the

initial slip surface. This means that it is good to make several analyses with different initial

slip surfaces and with different numbers of sections. Optimization of polygonal slip surfaces

can be also affected by local minimums of factor of safety. This means the real critical surface

does need to be found. Sometimes it is more efficient for the user to enter the starting

polygonal slip surface in a similar shape and place as an opitimised circular slip surface.


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Local minimums

Note: We often get complaints from users that the slip surface after the optimization

disappeared. For non-cohesive soils, where kPacef 0 the critical slip surface is the same

as the most inclined line of slope surface. In this case, the user should change parameters of

the soil or enter restrictions in which the slip surface cant pass.

Conclusion

The slope stability after optimization is:

Bishop (circular - optimization): 50,182,1 sSFSF

SATISFACTORY. Spencer (polygonal - optimization): 50,158,1 sSFSF

SATISFACTORY.

This designed slope with a gravity wall satisfies stability requirements.


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Solution:

For solving this task, use the GEO5 programSlope Stability. In this text, we will describe

the solution of this task step by step.

Construction stage 1: slope modeling, determination of safety factor of the existing

slope;

Construction stage 2: making the earth cut for the parking (only as a working stage)

Construction stage 3: construction of the wall, analysis of internal and external

stability;

Analysis results (Conclusion).

Construction stage 1: slope modeling

In the frame Settings, click on Select and then choose analysis settings nr. 1

Standard safety factors.

Then, model the interface of layers, resp. terrain using these coordinates.

Interface coordinates

Note: If data is entered incorrectly, it can be undone using the button UNDO (shortcut Ctrl-Z). In the same manner,we can use the opposite function REDO (Shortcut Ctrl-Y).

Buttons Undo and Redo

Then define the soil parameters and assign them to the profile.


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Soil


Unit weight3mkN

Angle of internal

friction ef Cohesion of soil

kPacef

SMSilty sand,

medium dense soil18,0 29,0 5,0

ML, MISilt with low or

medium plasticity, stiff

consistency, 8,0r

S

20,0 21,0 30,0

MSSandy silt,

firm consistency18,0 26,5 12,0

In the frame Stage settings choosepermanent design situation.

Analysis 1

stability of existing slope

Now open up the frame Analysis and run the verification of stability of the original

slope. As a verification method select Bishop and then perform the optimization of circular

slip surface. How to input slip surface and optimization principle is described in more detail

in the previous chapter and in HELP (F1).

Analysis 1stability of the original slope

The factor of safety of the original slope as analyzed by Bishop is:

50,126,2 sSFSF Satisfactory.


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Construction stage 2: earth cut modeling

Now add the second construction stage using the button in the upper left corner of the

window.

Toolbar Construction stages

Add the earth cut to the interface by adding individual points of the considered earth cut

(similar to adding points to the current interface) in the frame Earth cut. The excavation for

the sheeting wall is 0,5 m wide. After you are done with adding the points click on OK.

Coordinates of the earth cut

Note: If you define two points with same x coordinate (see picture), the program asks if you

want to add the new point to the left or right. The scheme of resulting input of the point is

highlighted with red and green color in the dialog window.

Frame Earth cut


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Construction stage 3: construction of the retainig wall

Now design the sheeting wall. In the frame Embankment add the points of the

interface of the embankment. With these we actually model the face of the structure of the

wall (see picture).

The points of embankment

Frame Embankment

Analysis 2internal stability of retaining wall

To verify the internal stability on the circular slip surface it is necessary to

model the structure as a stiff soil with ficticious cohesion, and not as rigid body. If it is

modeled as a rigid body, the slip surface cannot intersect the structure.


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Analysis 3external stability of retaing wall

Now add another analysis using toolbar in the left downward corner of the program.

Toolbar More Analyses

Before running the analysis of the external slope stability, add restrictions on the optimization

procedure using lines that the slip surface cant intersect when it executes the optimization

procedure (More info in HELPF1). In our example the restriction lines are the same as the

borders of the pile sheeting.

Analysis 4 - restrictions on the optimization procedure

Note: for analysis of external slope stability it is appropriate to input the retaining wall as asolid body. When the wall is modeled as a solid body, the slip surface doesnt intersect it

during the optimization evaluation.


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Analysis 4slope stability with earth cut and retaining wall (external stability)

From the results of external stability we can see, that the slope with the earth cut and

retaining wall is stable:

50,159,2 sSFSF Satisfactory.

Conclusion

The objective of this chapter was to verify the slope stability and design of earth cut

with retaining wall for the construction of a car park with ananalysis of internal and external

stability. The results of analyses are:

Analysis 1 (stability of existing slope): 50,126,2

sSFSF Satisfactory.

Analysis 2 (internal slope stability): 50,160,1 sSFSF Satisfactory.

Analysis 3 (external slope stability): 50,159,2 sSFSF Satisfactory.

This slope with earth cut and retaining wall from concrete (with width of 0,5 m) in terms of

long-term stability satisfies evaluation criteria.


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Note: this designed retaining wall would need to be checked for stress from the bending

moment of loading from active earth pressure. This bending moment can be analyzed in the

GEO5 programs Sheeting design and Sheeting Check.

For the same bending moment it is also necessary to design and check reinforcementsfor

example in program FIN ECConcrete 2D.


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Chapter 10. Design of geometry of spread footing

In this chapter, we are going to show you how to design spread footing easily and effectively.

Assignment:

Using EN 1997-1 (EC 7-1, DA1) standards, design the dimensions of a concentric spread

footing. Forces from columns act on the top of foundation. Input forces are:yxyx MMHHN ,,,,

.

The terrain behind the structure is horizontal; foundation soil consists of S-FSand with trace of

fines, medium dense soil. At 6,0 m is Slightly weathered slate. The GWT is also at a depth of 6,0 m.

The depth of foundation is 2,5 m below the original terrain.

Scheme of the assignmentanalysis of bearing capacity of spread footing

Solution

For solving this problem, we will use the GEO5 programSpread footing. Firstly, we input

all the data in each frame, except Geometry. In the Geometry frame, we will then design the spread

footing.


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Basic input

In the frame Settings, click on Select and then choose nr. 3 Standard EN 1997

DA1.

Frame Settingslist

Also select an analysis methodin this case Analysis for drained conditions. We will not

analyze settlement.

Frame Settings

Note: Usually, spread footings are analyzed for drained conditions= using the effective parameters of

soil ( efef c, ). Analysis for undrained conditions is performed for cohesive soils and short-term

performance using total parameters of soil ( uu c, ). According to EN 1997 total friction considered is

always 0u .

In the next step enter the geological profile, soil parameters and assign them to the profile.


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Soil, rock

(classification)

Profile

m

Unit weight

3mkN

Angle of internal

friction ef

Cohesion

of soil

kPacef

S-FSand with trace of

fines, medium dense soil0,06,0 17,5 29,5 0,0

Slightly weathered slate from 6,0 22,5 23,0 50,0

In the next step, open up the frame Foundation. As a type of foundation, choose Centric spreadfooting and fill in the dimensions such as depth from the original grade, depth of footing bottom,

thickness of foundation and inclination of finished grade. Also, input the weight of overburden, which

is the backfill of spread footing after construction.

Frame Foundation

Note: The depth of the footing bottom depends on many different factors such as natural and climatic

factors, hydrogeology of the construction site and geological conditions. In the Czech Republic the

depth of footing bottom is recommended to be at least 0,8 meters beneath the surface due to freezing.

For clays it is recommended that the depth be greater, such as 1,6 meters. When analyzing the bearing

capacity of a foundation, the depth of the foundation is considered as the minimal vertical distance

between the footing bottom and the finished grade.


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In the frame Load enter the forces and moments acting on the upper part of foundation:

yxyx MMHHN ,,,, . These values we obtained from a structural analysis program and we can import

them to our analysis by clicking on Import.

Frame Load

Note: For design of dimensions of spread footing, generally the design load is the deciding load. ,

However, in this case we are using the analysis settings EN 1997-1 - DA1, and you must enter the

value of service load too, because the analysis requires two design combinations.

Dialog window Edit load

In the frame Material, input the material characteristics of the foundation.

Skip the frame Surcharge, as there is no surcharge near the foundation.

Note: Surcharge around the foundation influences the analysis for settlement and rotation of the

foundation, but not bearing capacity. In the case of vertical bearing capacity it always acts favorably

and no theoretical knowledge leads us to analyze this influence.

In the frame Water enter the ground water depth as 6,0 meters.


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We are not going to enter a sand gravel bed because we are considering permeable

cohesionless soil at the of footing bottom.

Then open up the frame Stage settings and select permanent as the design situation.

Design of dimensions of the foundation

Now, open the frame Geometry and apply the function Dimensions design; with which

the program determines the minimum required dimensions of the foundation. These dimensions can be

edited later.

In the dialog window it is possible to input the bearing capacity of foundation soil Rd or select

Analyze. We will chose Analyse for now. The program automatically analyzes the foundation

weight and weight of soil below foundation and determines the minimum dimensions of the

foundation.

Dialog window Foundation dimensions design

Note: Design of centric and eccentric spread footing is always performed such that that the

dimensions of foundation are as small as they can be and still maintain an adequate vertical bearing

capacity. The option Input designs the dimensions of a spread footing based on the entered bearing

capacity of the foundation soil.


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Chapter 11. Settlement of spread footing

In this chapter, we describe how analysis of settlement and rotation of a spread footing is

performed.

Assignment:

Analyze the settlement of centric spread footing designed in last chapter (10. Design

of dimensions of spread footing). The geometry of the structure, load, geological profile and

soils are the same as in the last chapter. Perform the settlement analysis using the oedometric

modulus, and consider the structural strength of soil. Analyze the foundation in terms of limit

states of serviceability. For a structurally indeterminate concrete structure, of which the

spread footing is a part, the limiting settlement is: 0,60lim, ms mm.

Scheme of the assignmentanalysis of settlement of spread footing


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Solution:

For solving this task, we will use the GEO5 programSpread footing. We will use the

data from the last chapter, where almost all required data is already entered.

Basic Input:

The design of spread footing in the last task was performed using the standard EN

1997, DA1. Eurocodes do not order any theory for the analysis of settlement, so any common

settlement theory can be used. Check the setting in the frame Settings by clicking on Edit.

In the tab Settlement select the method Analysis using oedometric modulus and set

Restriction of influence zone to based on structural strength.

Dialog window Edit current settings

Note: The structural strength represents the resistance of a soil against deformation from a

load. It is only used in Czech and Slovak Republic. In other countries, the restriction of the

influence zone is described by percentage of Initial in-situ stress. Recommended values of

structural strength are from CSN 73 1001 standards (Foundation soil below the foundation)

In the next step, define the parameters of soils for settlement analysis. We need to edit

each soil and add values for Poissons ratio, coefficient of structural strength and oedometric

modulus, resp. deformation modulus.


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Soil, rock

(classification)

Unit

weight3mkN

Angle of

internal

friction ef

Coeff. of

structural

Strengthm

Deformation

modulus

MPaEdef

Poissons

ratio

S-FSand with

trace of fines,

medium dense soil

17,5 29,5 0,3 15,5 0,3

Slightly weathered

slate22,5 23,0 0,3 500,0 0,25

Analysis:

Now, run the analysis in the frame Settlement. Settlement is always analyzed for

service load.

Frame Settlement


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In the frame Settlement it isalso needed to input other parameters:

- Initial in-situ stress in the footing bottom is considered from the finished grade

Note: the value of in-situ stress in the footing bottom has influence on the amount of

settlement and the depth of influence zonea larger initial in-situ stress means less

settlement. The option of in-situ stress acting on the footing bottom depends on the time the

footing bottom is open. If the footing bottom is open for a longer period of time, the soil

compaction will be less and it is not possible to consider the original stress conditions of the

soil.

-

In Reduction coefficient to compute settlement, select the option Consider foundation

thickness effect (1).

Note: the coefficient 1

reflects the influence of the depth of the foundation and gives more

realistic results of the settlement

Results of analysis

The final settlement of the structure is 16,9 mm. Within an analysis of limit states ofserviceability we compare the values of the analyzed settlement with limit values, which are

permissible for the structure.

Note: The stiffness of structure (soil-foundation) has a major influence on the settlement. This

stiffness is described by the coefficient kif k is greater then 1, the foundation is considered

to be stiff and settlement is calculated under a characteristic point (located in 0,37l or 0,37b

from the center of the foundation, where l and b are dimensions of foundation). If coefficient

k is lower then 1, the settlement is calculated under the center of foundation.

-

Analyzed stiffness of foundation in direction is 10,137k . The settlement is

computed under the characteristic point of foundation.

Note : Informative values of allowable settlement for different kinds of structures can be

found in various standardsfor example CSN EN 1997-1 (2006) Design of geotechnical

structures.


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The Spread footing program also provides results for the rotation of the foundation, which is

analyzed from the difference of settlement of centers of each edge.

Rotation of the foundationprinciple of the analysis

Rotation in direction x : )1000(tan75,0

Rotation in direction y : )1000(tan776,1

Conclusion

This spread footing in terms of settlement satisfies evaluation criteria.

Settlement: 9,160,60lim, ssm [mm].

It is not necessary to verify rotation of this foundation.


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Chapter 12. Analysis of consolidation under embankment

In this chapter, we are going to explain how to analyze consolidation under a

constructed embankment.

Introduction:

Soil consolidation takes into account the settlement time (calculation of earth

deformation) under the effect of external (constant or variable) loads. The surcharge leads to

an increase in earth formation stress and the gradual extrusion of water from pores, i.e. soil

consolidation. Primary consolidation corresponds to the situation in which there is a complete

dissipation of pore pressures in soil, secondary consolidation affects rheological processes

in the soil skeleton (the so called "creep effect"). This is a time-dependent process influenced

by a number of factors (e.g. soil permeability and compressibility, length of drainage paths,

etc.). With regards to the degree of consolidation we distinguish the following cases of ground

settlement:

final settlement corresponding to 100% consolidation from the respective

surcharge

partial settlement corresponding to a particular degree of consolidation from

the respective surcharge

Assignment:

Determine the settlement value under the centre of an embankment constructed

on impermeable clay one year and ten years after its construction. Make the analysis using

CSN 73 1001 standards (using oedometric modulus), limit of influence zone consider using

coefficient of structure strength.

Scheme of the assignment - consolidation


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Solution:

The GEO 5 Settlement program will be used to solve this task. We are going to

model this example step by step:

1st construction stage interface modelling, calculation of the initial geostatic

stress.

2ndconstruction stage adding a surcharge by means of an embankment.

3rd up to 5th construction stages calculation of embankment consolidation

at various time intervals (according to the assignment).

Evaluation of results (conclusion).

Basic assignment (procedure): Stage 1

Check the "Perform consolidation analysis" field in the "Settings" frame. Then select

specific settings for calculation of the settlement from "Settings list". This setting describes

the analysis method for calculation of the settlement and restriction of influence zone.

Frame "Settings"

Note: This calculation considers the so called primary consolidation (dissipation of pore

pressure). Secondary settlement (creep), which may occur mainly with non-consolidated and

organic soils, is not solved within this example.

Then we enter the layer interface. The objective is to select two layers between which

the consolidation takes place.


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Frame "Interface"

Note: If there is a homogeneous soil, then in order to calculate the consolidation,

it is necessary to enter a fictitious layer (use the same parameters for the two soil layers that

are separated by the original interface), preferably at the depth of the deformation zone.

Then we define the "Incompressible subsoil" (IS) (at a depth of 10 m) by means of

entering coordinates similarly to interface modelling. No settlement takes place under the IS.

The soil parameters are entered in the next step. For soils being consolidated, it is

required to specify either the coefficient of permeability " k" or the coefficient of

consolidation "v

c ". Approximate values can be found in HELP (F1).

Dialog window "Modification of soil parameters"


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Soil


Unit weight3mkN

Poissons

Ratio

[ ]

Oedometric

modulus

[ ]MPaEoed

Coeff. of

structural

strength

[ ]

m

Coeff. of

permeability

[ ]daymk

Clayey soil 18,5 0,3 1,0 0,15100,1

Embankment 20,0 0,35 30,0 0,3 2100,1

Sandy silt 19,5 0,35 30,0 0,3 2100,1

Then we assign the soils to the profile. The frame surcharge in the 1st construction

stage is not taken into consideration, since in this example it will be represented by the actual

embankment body (in stages 2 to 5). In the next step, we shall enter the ground water table

(hereinafter the "GWT") using the interface points, in our case at ground level.

In the frame Stage settings, you can only modify layout and refinement of holes, so

leave the standard settings.

The first "Calculation" stage represents the initial geostatic stress at the initial

construction time. However, it is necessary to specify the basic boundary conditions for the

consolidation calculation in further stages. The top and bottom interface of the consolidating

soil is entered, as well as the direction of water flow from this layer i.e. the drainage path.

"Analysis" Construction stage 1


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"Stage 2 Embankment + Assignment"

Note: The embankment acts as a surcharge to the original ground surface. It is assumed thata well-executed (optimally compacted) embankment theoretically does not settle. In a

practice, settlement may occur (poor compaction, soil creep effect), but the program

Settlement does not address this.

In the "Analysis" frame enter the time duration of the2nd stagecorresponding to the

actual embankment construction time. The actual calculation of the settlement cannot be

performed yet because, when determining consolidation, it is first necessary to know

the whole history of the earthwork structure loading, i.e. all construction stages.

Frame "Analysis Construction Stage 2"


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Since the embankment is built gradually, we are considering the linear load growth

in the 2nd construction stage. In subsequent stages, the duration of the stage is entered (1 year

i.e. 365 days 3rd stage, 10 years i.e. 3,650 days 4th stageand the overall settlement 5th

stage) and the whole loading is introduced at the beginning of the stage.

The calculations are performed after enter the last construction stage, which is on the

"Overall settlement", is turned on (you can check it at any stage apart from the first one).

Frame "Calculation Construction Stage 5"


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Analysis results

Upon the calculation of the overall settlement, we can observe partial consolidation

values below the centre of the embankment. We have obtained the following maximum

settlement values in individual construction stages:

Stage 1: only geostatic stress settlement not calculated.

Stage 2 (surcharge by embankment): for 30 days29.2 mm

Stage 3 (unchanged): for 365 days113.7 mm

Stage 4 (unchanged): for 3,650 days311.7 mm

Stage 5: the overall settlement351.2 mm

"Analysis Construction stage 5 (Overall settlement)"

As we are interested in the embankment settlement after its construction,

we will switch to the results view in the 3rd and 4th stages (the button "Values") to "compared

to stage 2" which subtracts the respective settlement value.


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Documents

program calcul geotehnic