TYPES OF PILE FOUNDATION

• SHEET PILES: Equipped with a vertical interlocking system, sheet piles are long structural sections that create a continuous wall which is used to retain soil or water. The dependency of a sheet pile's ability to perform is on the geometry and the type of soil it is driven into. The pile transfers pressure from the high side of the wall to the soil in front of the wall.

• LOAD BEARING PILES: Load bearing pile are used to transmit the load of a structure through a soil layer which is too weak to support the structure. Pile acts as a column to transfer the load through the weak layer to a stronger layer. This type of pile is designed similar to a reinforced concrete column except the buckling is not considered in the design. 

• FRICTION PILES: Also called floating piles, friction piles receive their bearing capacity through shear stresses along the sides of the pile. They are best used in places where the hard layers of the soil are too deep to reach. Friction piles transfer the load from the topsoil to the bottom with the help of adhesion between pile surface and soil. 

• TIMBER PILES: Like the name suggests, this type of pile is made from timber obtained from teak, sal, deodar, etc. They can be square or circular in shape. 

Foundation selection based on soil types

FOUNDATION SELECTION BASED ON SOIL TYPES

Foundations are selected based on the type of soil reason being not every foundation can be supported on every soil type because of their varying textures and properties.

Foundations are selected based on the following types of soils: - 

1. Rocks

2. Uniform, firm and stiff clay 

3. Soft clay

4. Peat

1. Rocks: - Rocks, hard sound chalk, sand, and gravel with limited clay content and dense silty sand all fall under this group.

The foundations recommended for this soil type are:

1. Raft foundation

2. Pad foundation

3. Strip foundation

2. Uniform, firm and stiff clay: - This type is divided into 3 cases:

•  If the foundation is adjacent to the vegetation or where the presence of vegetation is unimportant.

The foundations recommended for this case are: -

1. Raft foundation

2. Strip foundation

3. Pad foundation

•  Where there are trees, hedges and bushes near the foundation or where there is a proposal to plant these plants near the structure in the future.

The foundations recommended for this case are: -

1. Concrete piles supporting reinforced concrete ground beams and precast concrete floor.

2. Raft foundation.

3. Specially designed trench fills in certain clay soil based on the foundation location relative to trees. 

4. Concrete piles carrying in situ concrete slab.

• Where trees are felled just prior to the start of foundation construction

The foundations recommended for this case are: -

1. Strip foundation

2. Raft foundation

3. Reinforced concrete pile in previously tree root zone

3. Soft Clay: - soft clay, soft silty clay, soft sandy clay and soft silty sand all fall within this group. 

The foundations recommended for this case are: -

1. Pile to firmer strata below

2. Wide strip footing

3. Raft foundation

4. For smaller projects use pier and beam foundation to firm strata.

4. Peat: - The foundations recommended for this case are as follows:

1. Raft foundation for the case where firm strata is not available at reasonable depth but there is hard surface crust within 3-4mm thick of suitable bearing capacity.

2. Concrete piles extended to the firm soil layer below.

3. For small projects, pad and beam foundation are taken to the firm strata below.

USES OF DIFFERENT TYPES OF FOOTINGS

 USES OF DIFFERENT TYPES OF FOUNDATIONS/ FOOTINGS

The different types of foundations/footings serve uses in their own separate ways.

1. STRAP FOOTING:-When the distance between the column is so great that the combined trapezoidal footing becomes fairly narrow, with a strong bending moment, a strap footing may be employed.

2. ISOLATED FOOTING:- When single - columns are positioned at a great distance, an isolated footing is one of the most commonly utilized type of foundation. An isolated footing must be built to avoid exceeding its bearing capacity, offer safety from overturning or sliding, and keep the ground from setting.

3. SPREAD FOOTING:- When compared to a load bearing foundation, a spread footing/foundation has a wider bottom component; the wider bottom "spreads" the structure's weight across a larger area for greater stability. Spread footings are used to support a foundation or piers beneath a structure.

Spread foundation can also be used in the following ways: -

CONCRETE SPREAD FOOTINGS:- Spread footings are used to support a building's foundation or piers. Spread footings, which are made of concrete and reinforced with steel, provide additional support.

SPREAD FOOTING WITH PIER:- Spread footings are used to support a foundation or piers beneath a structure. Spread footings are made of concrete and reinforced with steel to provide additional support. 

4. RAFT FOOTING:- Raft foundations are commonly used to support structures such as residential or commercial buildings in poor soil conditions, storage tanks, silos, and large industrial equipment foundations, among other things.

5. COMBINED FOOTING:- When only a single column appears in the foundation plan of a project, this style of footing is preferred. The term "combined footing" refers to a foundation that can carry two or more column loads. These might be rectangular or trapezoidal in plan and can be continuous.