Field investigation of the effect of installation method on the shaft resistance of piles in clay

This paper presents the results of a series of field experiments performed to study the effect of installation method on the shaft resistance developed by a pile installed in soft clayey silt. Tests were performed on piles which experienced different levels of cyclic loading during installation. The test results indicate that the radial total stress, pore water pressure and shear stress on the pile shaft during installation, were strongly affected by the installation procedure; all three were found to increase when the jacking stoke length used during installation increased (or the number of cyclic load applications decreased). However, equalised radial effective stresses which control the long-term pile shaft capacity were found to be insensitive to the installation method. A simple expression is proposed which requires the results of a cone penetration test, laboratory measurements of the interface friction angle and the pile geometry is proposed to calculate the shaft resistance.