Pile Foundation and its Components:

A pile foundation is a type of deep foundation that is used to transfer loads from the structure to a deeper soil or rock strata. The pile foundation consists of three main components:

1. Pile Shaft: It is the part of the pile that is embedded in the soil and transfers the load to the soil.

2. Pile Toe: It is the bottom end of the pile that provides end bearing resistance.

3. Pile Head: It is the top end of the pile that connects the pile to the structure.

Skin Friction and End Bearing:

Two main types of resistance are encountered by piles, skin friction and end bearing. Skin friction is the frictional resistance developed along the surface of the pile shaft due to the adhesion and cohesion between the pile and the soil. End bearing resistance is the resistance developed at the pile toe due to the bearing capacity of the underlying soil or rock strata.

Separation of Skin Friction and End Bearing:

The separation of skin friction and end bearing is necessary to estimate the pile capacity accurately. This is because both types of resistance occur simultaneously and the contribution of each type depends on the soil conditions and the pile geometry. The separation of skin friction and end bearing can be achieved by performing a cyclic loading test.

Cyclic Loading Test:

A cyclic loading test involves applying a series of loads to the pile and measuring the pile deformation and the soil reaction. The test is performed by applying a cyclic load to the pile and monitoring the load and the deformation. The cyclic loading test helps in separating the skin friction and end bearing because:

1. During the initial stage of loading, the skin friction resistance dominates, and the pile deformation is primarily due to the bending of the pile.

2. As the load is increased, the end bearing resistance becomes dominant, and the pile deformation is primarily due to the axial compression.

3. By analyzing the load-deformation curve obtained from the test, the skin friction and end bearing can be separated and used to estimate the pile capacity accurately.

Conclusion:

In pile foundation, the skin friction and end bearing are separated by performing a cyclic loading test. The separation of skin friction and end bearing is necessary to estimate the pile capacity accurately.