Pile installation effects in natural soft clays: A semi-analytical solution using strain path method

This paper develops a semi-analytical solution for pile penetration in natural soft clays using the strain path method (SPM). The stress-strain behavior of soils is characterized by the S-CLAY1S model, which can capture the anisotropic evolution and destructuring nature of soft clays. By integrating the S-CLAY1S model into the theoretical framework of the SPM, a set of ordinary differential equations is formulated with respect to the vertical coordinate of soil particles. The distribution of excess pore water pressure (EPWP) following pile installation is approximated through one-dimensional (1D) radial integration around the pile shaft. The distribution of stresses and EPWP, along with the evolution of fabric anisotropy within the soil surrounding the pile, is presented to illustrate the response of pile penetration in natural soft clays. The proposed solution is validated against existing theoretical solutions using the SPM and cavity expansion method (CEM), along with experimental data. The findings demonstrate that the SPM reveals lower radial effective stresses and EPWP at the pile shaft than that of CEM. Pile penetration alters the soil's anisotropic properties, inducing rotational hardening and affecting post-installation stress distribution. Soil destructuration eliminates bonding among particles near the pile, resulting in a complete disruption of soil structure at the pile surface, which is particularly pronounced for higher initial soil structure ratios. Minimal variation was observed in the three principal stresses and shear stress on the cone side surface as the angle increased from 18° to 60°, except for a slight reduction in EPWP.