5 - Pile Design in Clay Soils

Abstract

Two types of forces act on piles: end-bearing acts on the bottom of the pile and skin friction acts on the sides of the pile. To compute the total load that can be applied to a pile, one needs to compute the end bearing and the skin friction acting on sides of the pile. It is usually assumed that ultimate skin friction is independent of the effective stress and depth. In reality, skin friction is dependent on effective stress and cohesion of soil. The skin friction acts on the perimeter surface of the pile. The total capacity of a pile depends on many parameters: skin friction, end-bearing capacity, negative skin friction, pile properties (toe area, perimeter area, pile material, pile flexibility), driving process (driven, jetted down, vibrated down, or jacked down), hammer type, hammer weight, and stroke for driven piles, and loading type (cyclic and vibratory loads reduce the pile capacity).