Drained-Undrained Shaft Resistance of Piles in Soft Clays

Abstract

The determination of the stress distribution around driven piles in soft clays constitutes a complex problem. The stress distribution is affected by a range of factors such as soil permeability, soil strength, sensitivity, remoulding, distance from adjacent piles and number of piles. The mechanisms of pile installation and subsequent consolidation are investigated by considering that pile installation may be represented by the expansion of a long vertical cylindrical cavity. The stress paths followed by typical soil elements at the soil–pile interface are analyzed by means of the theoretical relationships obtained during the undrained expansion of a cylindrical cavity in soft cohesive soils and modified to take into account the severe remoulding caused by pile installation. It is shown that the shaft resistance of driven piles may be calculated by considering either a drained stress path or an effective stress path during undrained loading. It is also shown that soft clay remoulding caused by pile driving is a major factor that must be taken into account for a reasonable estimation of the limiting skin friction.