Pile foundation

PILE FOUNDATION PPT

1. Seminar Presentation on PILE FOUNDATION Submitted to- Mr. S.C . Verma Civil Engg. Department COER Submitted By:- Akash Deep Singh Civil Engg.-4 th year Section – E Roll No.- 06

2. What is pile foundation. . . .? The pile foundation is used to describe a construction for the foundation of a wall or a pier, which is supported on the pile. Where it is placed …? The piles may be placed separately or they may be placed in the form of cluster throughout the length of the wall . Where it is adopted …? Piles are adopted when the loose soil extended to a great depth . The load of the structure is transmitted by the piles to hard stratum below or it is resisted by the friction developed on the sided of the piles.

3. Application of piles………. The piles are applicable at the places where, The load coming from the structure is very high & the distribution of the load on soil is uneven. The subsoil water level is likely to rise or fall appreciably. The pumping of subsoil water is too costly for keeping the foundation trench in dry condition. The construction of raft foundation is likely to be very expensive or it is likely to practically impossible. The piles are considered to be long when their length exceeds 30 meters. The structure is situated on sea shore or river bed and the foundation is likely to adopted by the scouring action of water. The piles are also used as anchors . They may be designed to give lateral support or to resist an upward pressure of uplift pressure.

4. Based on the function; 1. End bearing Pile 2. Friction Pile 3. Compaction Pile 4. Tension Pile or U plift Pile 5. Anchor Pile 6. Fender Pile and Dolphins 7. Batter Pile 8. Sheet Pile Based on the material & composition; 1. C oncrete Pile 2. Timber Pile 3. Steel Pile 4. Composite Pile: Concrete & Timber, Concrete & Steel Based on the method of installation; 1. Driven Pile 2. Cast-in-situ Pile 3.Driven and cast- in- situ Pile Classification of Piles:

5. Loads coming on pile foundations All the loads from the super structure like, - Live loads - Dead loads - Wind loads - Seismic load The loads from the surrounding soil in case of seismic event. Water loads in case of off-shore structure.

6. Types of pile Load bearing piles Non-load bearing piles Load bearing piles :- It bear the load coming from the structure. The Piles are generally driven vertically or in near vertical position. When a horizontal forces to be resisted , the inclined piles may be driven in an inclined position and such inclined piles are termed the batter piles Load bearing piles are divided into, Bearing piles Friction Piles

7. Bearing piles This piles penetrate to through the soft soil and their bottoms rest on a hard bed . Thus, they are end bearing piles and act as columns or piers. The soft ground through which the piles pass also gives some lateral support and this increases the load carrying capacity of the bearing piles.

8. Bearing Piles P base Side Friction End Bearing Pile Load, P

9. Friction piles When loose soil extends to a great depth, the piles are driven up to such a depth that the frictional resistance developed at the sides of the piles equals the load coming on the pile s. G reat care should be taken to determine the frictional resistance offered by the soil and suitable factor of safety should be provided in the design .

10. Friction Piles End Bearing Pile Load, P Side Friction P base

11. Pile Driving The process of forcing the piles into the ground without excavation is termed as the pile driving. The piles should be driven vertically . However, a tolerance of eccentricity of 2 % of the pile length is permissible. The eccentricity is measured by means of plumb bob . The equipments required for pile driving are as follows, Pile fames Pile hammers Leads Winches Miscellaneous

12. Piles are commonly driven by means of a hammer supported by a crane or a special device known as a Pile Driver . Hammers adopted for driving the pile are of the following types : 1. Drop hammer 2. Single acting hammer 3. Double acting hammer 4. Diesel hammer 5. Vibratory hammer. Pile Driving

13. What is ultimate load bearing capacity? What is allowable load and how is it determined? Ultimate load bearing capacity of a pile is defined as the maximum load which can be carried by a pile and at which the pile continues to sink without further increase of the load. The allowable load is the safe load which the pile can carry safely, which can be determined from ultimate load bearing capacity dividing by suitable F.O.S. Load carrying capacity of Pile:

14. Factors affecting pile capacity Surrounding soil Installation technique (like driven or bored). Method of construction (like pre cast or cast in situ). Location of pile in a group. Spacing of piles in a group. Symmetry of the group. Shape of pile cap Location of pile cap (like above soil or below soil). Drainage condition in soil.

15. The load carrying capacity of a pile can be determined by the following methods: Dynamic formulae Static formulae Pile load tests, and Penetration test Methods of determining ‘Load carrying capacity’

16. Embedded Length = D Q u = Ultimate Bearing Capacity Q s = fA s f = Unit Frictional Resistance A S = Shaft Area (Pile surface area) q b = Unit Bearing Capacity A b = Area of Pile Base Q b = q b A b Bearing capacity of piles from soil parameters: Static Formula Method ( Q u = Q b + Q s ) Pile capacity Theoretical Approach :- In this approach the pile capacity is calculated using some formula in which the soil data is fed for obtaining the capacity.

17. Non - Load bearing piles This piles are used to function as the separating members below ground level and they are generally not designed to take any vertical load. This piles are also known as the sheet piles . The materials used for the construction of non load bearing piles are, Timber sheet piles Steel sheet piles Concrete sheet piles

18. Non - Load bearing piles Non load bearing piles are used for the following purposes. To isolate foundations from the adjacent soils . This prevents escape of soil and passage of shocks and vibrations to adjoining structure. To prevent underground movement of water like to construct a cofferdam, it requires a water tight enclosure in the construction of foundation under water. To prevent the transfer of machine vibrations to the adjacent structures . To construction of retaining wall . To protect the river banks. To retain the sides of foundation trenches .

19. Negative friction is a down- ward drag acting on a pile due to the downward mo - vement of the surrounding compressible soil relative to the pile. It is shown in figure aside. Figure shows the pile pass- ing through a recently con- structed cohesive soil fill . The soil below the fill is completely consolidated under its overburden pressure . Negative Skin Friction

20. Negative Skin Friction will occur due to the following reasons: When the surrounding compressible soil has been recently filled . If the fill material is loose cohesion less soil. By lowering the ground water which increases the effective stress causing consolidation of the soil with resultant settlement and friction force being developed on the pile. It also occurs when the fill is over the peat or a soft clay stratum. Cont...

21. Factors governing the selection of piles They are: Length of the pile in relation to the load and type of soil, Characters of structure, Availability of the materials, Types of loading, Factors causing deterioration, Ease of maintenance, Estimated cost of types of piles, taking into account the initial cost, life expectancy and cost of maintenance and, Availability of funds. Selection of Pile