Evolution of mechanical properties of soils subsequent to a pile jacked in natural saturated clays

The mechanical properties of soils adjacent to a jacked pile significantly affect the bearing capacity and settlement of the pile. This paper investigates the evolution of the mechanical properties of the remolded soil surrounding a jacked pile by considering in-situ properties of natural clays, pile installation effects and variable coefficient of consolidation. The pile installation process is modeled by the undrained cylindrical cavity expansion. The distribution of excess pore pressures around the pile is derived by adopting the K₀-based anisotropic modified Cam-clay (K₀-AMCC) model, which can incorporate the initial stress anisotropy and the initial stress-induced anisotropy of natural clays. The Terzaghi's radial consolidation theory is further developed by introducing a variable coefficient of consolidation to the governing equation, which is solved by the variable separation method. The predicted results are in good agreement with the published test data. The variations of the mechanical properties of the remolded soil are studied with different variable coefficients of consolidation and the in-situ properties. The calculated results show that the variable coefficient of consolidation plays a significant role in the dissipation rate of excess pore pressures. The undrained shear strength considering thixotropic effect and the shear modulus of the remolded soil increase more rapidly with larger values of the introduced parameter α (related to the variable coefficient of consolidation). Moreover, the overconsolidation ratio has a pronounced effect on the undrained shear strength and the shear modulus of the remolded soil after pile installation.