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PILE FOUNDATION

Foundations are structural components used to support columns and transfer loads to the underlying Soil.

Foundations

FOUNDATIONS

Shallow Deep

Isolated footing

Combined footing

Strap

footingWall

footingRaft

footing Caissons Pile

Pile foundations are the part of a structure used to carry and transfer the load of the structure to the bearing ground located at some depth below ground surface.

A pile is a slender structural member made of steel, concrete or wood.

A pile is either driven into soil or formed in-situ by excavating a hole and filling it with concrete.

PILE FOUNDATION

As with other types of foundation, the purpose of a pile foundation is: To transmit a foundation load to a solid ground. To resist vertical, lateral and uplift load .

Piles can be Timber Concrete Steel Composite

FUNCTION OF PILES

When the strata below the ground surface is very weak to support load transmitted by the structure.

For the transmission of structural loads through deep water to a firm stratum.

Where the soil is water-logged. When stratum of required bearing capacity is at greater

depth.When the soil is highly compressible.

NECESSITY OF PILE FOUNDATION

Load on the pile is more than the designed load. Displacement of reinforcement during casting. Bearing pile resting on a soft strata. Improper choice of the type of pile. Insufficient reinforcement in the pile. Decay of timber piles due to attack by insects. Buckling of piles due to inadequate lateral support. Defective method adopted for driving the pile. Incorrect assessment of the bearing capacity of the pile. Lateral forces not considered in the design of piles.

CAUSES OF FAILURE OF PILES

Physical properties of the soil at the site.Depth to a stratum capable of supporting the piles.Possibility of variations in the depth to a supporting

stratum.Availability of materials for piles.Number of piles required.Facilities for driving piles.Comparative costs in place.Types of structures adjacent to the project.

FACTORS AFFECTING SELECTION OF PILES

Based on material

Based on method of construction / installation

Based on mode of transfer of loads

Based on use

Based on displacement of soils

CLASSIFICATION OF PILES

Concrete PilesSteel PilesTimber PilesComposite Piles

CLASSIFICATION BASED ON MATERIAL

Driven pilesDriven and cast-in-situ pilesBored and cast-in situ pileJacked piles

CLASSIFICATION BASED ON METHOD OF CONSTRUCTION

End bearing piles Friction/Floating piles Combined end bearing piles

CLASSIFICATION BASED ON MODE OF TRANSFER OF

LOADS

Load bearing pilesCompaction pilesTension pilesSheet pilesFender pilesAnchor piles

CLASSIFICATION BASED ON USE

Displacement pilesNon-displacement piles

CLASSIFICATION BASED ON DISPLACEMENT OF SOILS

Combinations of vertical, horizontal and moment loading may be applied at the soil surface from the overlying structure.

For the majority of foundations the loads applied to the piles are primarily vertical.

For piles in jetties, foundations for bridge piers, tall chimneys, and off-shore piled foundations the lateral resistance is an important consideration.

LOADS APPLIED TO PILES

H

VM

Drop hammerSteam-hammerBoringScrewingWater jet

PILE DRIVING METHODS

Hammer is raised by a rope or a steel cable. Then it is allowed to drop on pile cap. The weight of drop varies from 230-1800 kg. Weight depends on the shape and length of pile and

the nature of the ground. Takes a lot of time.

DROP HAMMER

DROP HAMMER METHOD

A heavy hammer is dropped on to the pile through a small height but in quick succession.

A steam cylinder and piston is used. Steam pressure and the rate of hammer blows are

kept uniform. Steam hammers are of two types:

Single Acting type Double Acting type

STEAM HAMMER

Sometimes, piling is done by boring holes of suitable diameter to the required depth and then dropping piles in them.

Generally cast-in-situ piles are laid by this method.

SCREWINGScrew piles and disc piles are generally driven by this

method.They are driven into the ground by turning them round

and round in one direction with big levers.

BORING

INSTALLATION BY BORING

Pile driving can also be done displacing the material at or near the foot of the pile by means of one or more water jets under pressure.

Sometimes, hammer may be used to force the pile rapidly into the ground.

The pressure of the jet should be sufficient to displace the soil for driving the piles quickly and satisfactorily.

WATER JETS

Provides a common solution to all difficult foundation site problems.

Can be used for any type of structure . Can be used in any type of soil. Now-a-days pile foundation is vastly in use instead

of well and caisson foundation.

ADVANTAGES OF PILE FOUNDATIONS

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