Friction Capacity of Piles Driven into Clay

Several studies on axial pile capacity in clays have shown that the average frictional resistance, expressed as a fraction of the average undrained shear strength or average effective overburden pressure, decreases with increasing pile penetration. Procedures to compute shaft friction are reviewed, and the effect of pile length on the development of shaft friction on piles in clay is examined in terms of the relative pile-soil stiffness and lateral pile movements during installation. Correlations are developed to relate shaft friction coefficients α,β,λ, to pile length, relative pile-soil stiffness, and soil stress history. Procedures are recommended to compute the friction capacity of piles in clay.