Explanation:

In the case of cohesive soil, which is a type of soil with fine particles that stick together, the surface area of the pile is neglected for individual pile action. This means that the surface area of the pile does not play a significant role in the behavior of the pile in cohesive soil.

Reasoning:

The reason for neglecting the surface area of the pile in cohesive soil is primarily due to the nature of cohesive soil itself. Cohesive soil has the ability to develop shear strength due to the cohesive forces between its particles. These cohesive forces allow the soil to resist deformation and maintain its shape.

Frictional Resistance:
Frictional resistance refers to the resistance offered by the soil to the movement of the pile. In cohesive soil, the cohesive forces between the soil particles are much stronger than the frictional forces. Therefore, the frictional resistance is negligible compared to the cohesive forces.

Shear Strength of Soil:
Shear strength is the ability of soil to resist shear stresses. In cohesive soil, the shear strength is primarily derived from the cohesive forces between the soil particles. These cohesive forces contribute to the shear strength of the soil and allow it to resist deformation.

Surface Area of Pile:
The surface area of the pile refers to the area of contact between the pile and the surrounding soil. In cohesive soil, the cohesive forces between the soil particles dominate the behavior of the soil-pile system. The surface area of the pile is relatively small compared to the cohesive forces acting on the soil particles. Therefore, the surface area of the pile is neglected for individual pile action in cohesive soil.

Conclusion:
In cohesive soil, the behavior of the pile is primarily governed by the cohesive forces between the soil particles. The frictional resistance and surface area of the pile are negligible compared to the cohesive forces. Therefore, the surface area of the pile is neglected for individual pile action in cohesive soil.