Load Bearing Piles

1. Cast iron piles. 

Cast iron piles are hollow tubes of cast iron having inner diameter 20 to 40 cm and

wall thickness 20 to 30 mm. These are generally 4 metres in length and for longer lengths

these are joined by a suitable device. Cast iron being a brittle material, these piles are

provided with helical screws at the lower end and the whole assembly is rotated to drive

the pile inside the soil. Piles with helical screws are generally known as screw piles. Cast

iron piles are suitable for shallow foundations and are suitably employed for the

foundations of marine structures, light weight bridges and buoys anchors.

2. Cement concrete piles

These are of the following types :

A. Cast-in-situ piles

These piles are cast with cement concrete at the place where  

these have to carry superimposed load. For casting the pile, a hole is driven by excavating

with an Auger or driving a casing. The hole is then filled up with cement concrete. As

these piles are generally driven vertically, No reinforcement is needed. If the casting is

left in position, the pile is known as cased cast in-situ concrete pile and if the case is

withdrawn, the pile is known as uncased cast in-situ concrete pile.

B. The uncased cast-in-situ piles

 The uncased cast-in-situ concrete piles are of the following

types:

(i) Simplex pile 

 A hollow cylindrical steel casing with one pointed iron shoe

attached to its bottom is driven into the ground to the desired depth. Concrete is then

poured into the casing pipe for a depth of about one metre and compacted. The casing

pipe is lifted up for a distance of one metre. In this way entire length of the hole is filled

up with compacted concrete which acts as a pile.

(ii) Frankie Pile 

It consists of an enlarged base and corrugated stem. Initially 60

cm to 90 cm bottom portion of the casing pipe is filled with concrete and compacted by

dropping a hammer to provide a solid plug at the end. The casing is then driven in by hammering the concrete plug till it reaches the desired depth. Now the casing is lifted to

a small distance and the concrete is forced by the hammer blows. Successive layers of

concrete are then poured and compacted, and simultaneously the casing is lifted.

(iii) Pedestal pile A concrete pile with a pedestal at the bottom end is known as

pedestal pile. The pile may consist of plain cement concrete or reinforced cement

concrete.

(iv) Pressure pile A pile which is made by pouring cement concrete inside a casing

pipe in layers of 30 cm, and each layer being compacted by compressed air, is called a

pressure pile. The casing is gradually lifted. Such piles can resist shocks and Vibrations

to a greater extent.

(v) Vibro pile A hollow steel tube with a cast iron shoe at its bottom, is driven into

the ground to the desired depth. The casing is filled with fresh cement concrete. The

casing is then removed by pulling upward and hammering downward. Such piles are cast

with a rapid speed and generally these consist of dense and uniform concrete.

(vi) Under-reamed pile In soils which experience alternate swelling and shrinkage

due to changes in its moisture content, under-reamed piles are used for transferring

heavy loads. Under-reams are provided at distances 1.5 it apart.

B. Cased cast in-situ concrete piles The cast-in-situ concrete piles in which casing

is left in the ground, are of the following types : .

(A) Raymond pile

In this type of piles, a corrugated thin steel sheet tapered shell  

is driven into the ground with a collapsible steel mandrel inside it, to a desired depth. The

reinforcement cage is inserted into the sheet and cement concrete is poured into it. These

piles are suitable for lengths varying from 6 to 15 metres.

(B) Monutube pile 

In this type of piles, tapered steel shell without any mandrel is

used as casing. It is driven into the ground to desired depth. Reinforcement case is

inserted into the shell and cement concrete is then poured into it.

(C) Mac-Arthur pile

In such piles heavy steel casing is driven into the ground with

a core inside it to a desired depth. The core is then pulled out and a corrugated steel shell

is inserted. Finally cement concrete is poured and outer casing is withdrawn.

(D) Button bottom pile

In such piles, a button shaped bottom is used at the lower

end of the steel casing which is driven into ground to a desired depth. A corrugated steel

shell is lowered into the steel casing. The steel casing is removed and cement concrete

is poured into the shell.

3. Sand piles

In this type of piles, holes are driven into ground to desired depth and sand

is filled in the holes. Such piles improve the bearing capacity of the soil. If instead of sand,

gravels are used, the piles are called gravel piles.

4. Timber piles

In this type of pile, piles of hard and strong timber pile carries a cast iron

shoe and upper end is provided with a steel plate to receive hammering stress. If a number of timber piles are used, their tops are provided with a concrete cap known as pile cap. 

5. Steel piles

Steel piles may be either H piles, box piles or circular tube piles.

(a) H-piles

These piles are suitably used in hard soil by driving to desired depth  

by hammering. These are generally used in retaining walls.

(b). Box piles

 These piles are generally rectangular, square or octagonal in shape.

These consist of deep beams which offer adequate frictional resistance and end

resistance.