S.N.P.I.T. & R.C.

UMRAKH

Pile FoundationAssis. Professor Neetu Yadav

Presentation By

Mehta Mrunali- 130490106064

Modi Nagma- 130490106065

Nakrani Akash- 130490106066

Nikam Sejal- 130490106067

Pile Foundation

Contents:-Introduction-Uses of pile-Selection of type of pile-Types of pile-Pile spacing-Group of piles-Efficiency of group of pile-Pile hammer-Micro piling-Causes of failure of piles

Introduction:Pile foundations are divided in two parts:1. deep foundation2. Shallow foundationPile foundation is that type of foundation in which the loads are taken to a law level by means of vertical members which may be of timber, concrete , or steel.

Uses of piles:-Pile foundation is generally used when simple spreadfoundation at a suitable depth is not possible eitherbecause the stratum of required bearing capacity is at agreater depth are encountered.-piles are used for foundation for building, bridges, andwater front installation.-They are also used for structures in the area wherecanals, deep drainage lines, etc.

Factor affecting selection of piles:1. Location and type of structures.2. Ground condition3. Durability4. Cost consideration

Classification of piles based on their functions:

1. End bearing piles

2. Friction pile

3. Compaction pile

4. Tension pile

5. Anchor pile

6. Fender pile

7. Better pile

8. Sheet pile

End bearing piles: If the piles are driven into the ground until a hardstratum is reached and the piles act as a pillarssupporting the super structure and transmitting the loadto the hard ground.

Friction pile When loose soil extended to a great depth, pile are

driven up to a such a depth that frictional resistance developed at the sides of the piles equals the load coming on the piles

Fender pile: Fender piles are used to protect water front

structure against impact from ships or other floating

objects.

Sheet pile: They are used to bulk heads or as impervious cutoff

to reduce seepage and uplift under hydraulicstructure.

Depending upon the materials used in construction of load bearings piles are classified as:•Cast iron pile• Cement concrete pile1.Pre cast piles2.cast-in-situ piles3. Prestressed concrete piles• Sand pile• Steel pile• Timber pile•Wrought-iron pile

Precast pile: Precast concrete piles are those which are

manufactured in a factory or at a place away from the construction site, and then driven into the ground at the place required.

Cast-in-situ concrete piles: In this type of concrete piles, a bore is dug into the

ground by inserting. This bore is then filled with cement concrete after placing reinforcement, if any.

Common types of uncased cast-in-situ piles:

1. Simplex piles

2. Franki piles

3. Vibro piles

4. Pedestal piles

5. Pressure piles

Pedestal piles: This type of piles are used where thin bearing

stratum is reached with reasonable depth. Thepedestal of the pile gives the effect of spreadfooting on this comparatively thin bearing.

Franki pile: In this type of pile, a plug of dry concrete gravel is

formed on the ground by heavy removable pipe shell.

Timber pile: Thee piles are prepared from trunks of trees. They

may be circular or square. They are 30 to 50 cm indiameter with a length not exceeding 20 times itstop.

Sand piles: These piles are formed by making holes in the

ground and then filling them with sand. If sand iskept confined, it possesses great crushing strengthand becomes incompressible.

Non-Load Bearing pile:This type of piles are used as a separating members

below ground level and they are generally not designed totake any vertical load.

•Purpose:-To isolate foundation from adjacent soil.- To construct retaining wall in docks, wharfs etc.-To protect river banks.-Intake supplies.

Under-reamed pile:- The under reamed pile provide an ideal solution to

foundation in black cotton soil or other similar type ofexpansive soil.

A pile having one bulb at a base is known as a singleunder reamed pile.

A load bearing capacity of pile can be increased byincrease in the number of bulb at the base.

The diameter of an under reamed pile varies from 20 cmto 50 cm. And bulb diameter varies from 2 to 3 times thediameter of pile

Method of construction:-The equipment for the construction of pile consists of auger boring guide, spiral auger with extension road, under-reamer with bucket and concreting funnel etc.-The auger should be rotated slowly with a constant downward pressure and taken out when it is full with soil. -The holes for casting pile in the ground may be bored by using hand augers.-For deeper borings , the length of the auger can be increased by adding suitable extension rods or pipes.-In sites where the sub soil water table is high, bentoniteslurry are used to retain the sides of the bore hole against collapse.-After the pile holes are ready for concreting , the reinforcement cages are lowered in the holes and concrete is poured by the use of funnel.

Pile spacing:The spacing of the pile is the centre to centre distance

between two successive piles.

Factors:-The nature of soil through which the pile is driven.-The obstructions during pile driving.-The type of pile.-The area of cross section.-The depth of penetration.-The centre to centre distance of pile in a group.-The material of pile.

Group of piles:Sometimes the piles are arranged in close spaced group.

when the piles are driven to the required depth, their topsare cutoff to a same level and then the pile cap is provided asin figure.

- The piles are forming the group of pile may be arranged in square, rectangular, triangular or circular as per the requirement- In case of single pile, a small pressure is developed in the

surrounding soil.- The bearing capacity of a pile group may not be necessarily equal to the sum of the bearing capacity of individual piles forming a group.- The cost of friction pile, the centre to centre distance between successive piles should be 105cm. or the perimeter of the pile, whichever is greater.

Efficiency of group of pile:The efficiency of a pile group is taken as the ratio of the

average load per pile, When the failure of group occurs to the load at failure of a comparable single pile.It is determined by two methods:•converse Labbore equation.•Field rule.

PILE HAMMER:

1.Drop hammer:

The drop hammer in the pile driving equipment consists of a heavy ram in between the leads. The ram is lifted up to a certain height and released to drop on the pile. This type is slow and therefore not in common use

2. Single acting hammer In a single acting hammer a heavy ram is lifted up

by steam or compressed air but dropped by its ownweight. The energy of a single acting hammer isequal to the weight of the ram times the height offall.

3. Double acting hammer: The double acting hammer employs steam or air for

lifting the ram and for accelerating the downwardstroke. The energy of a double acting hammer isequal to weight of ram or effective pressure of 1times the height of fall.

4. Diesel hammer: The diesel hammer is a small, light weight and

highly mobile. They use gasoline for fuel. To start the operation, the ram is raised, and the fuel is injected. As the ram released, the ram falls and compressed air and fuel.

Micro piling: Micro piling is to the demand for innovative

techniques for underpinning historic buildings and mounments that has sustained damage with time. The micro piling systems used today are evolution from the basic small diameter, cast-in-situ pile.

Causes of failure of piles: Absence of statistical data regarding the nature of soil

strata through which the piles are to be driven.

Actual load coming on the pile being more than thedesign.

Bad workmanship in case of the cast-in-situ cementconcrete piles.

Attack by insects, etc. on wooden piles.

Breakage due to over driving especially in case of thetimber piles.

Buckling of piles due to removal of side support,inadequate lateral supports, etc.

Improper choice of the pile.

Pressure of soft strata just below the tips of piles.

Improper choice of the method of the driving the pile.