Undrained cylindrical cavity expansion in clays with fabric anisotropy and structure: Theoretical solution

Abstract

ABSTRACT: This paper presents a novel, exact, semi-analytical solution for the quasi-static undrained expansion of a cylindrical cavity in soft soils with fabric anisotropy and structure. The assumed constitutive model is the S-CLAY1S model, which is a Cam clay type model that considers fabric anisotropy that evolves with plastic strains, structure and gradual degradation of bonding (destructuration) due to plastic straining. The solution involves the numerical integration of a system of seven first-order ordinary differential equations, three of them corresponding to the effective stresses in cylindrical coordinates, other three corresponding to the components of the fabric tensor and one corresponding to the amount of bonding. The solution is validated against finite element analyses and analytical limit asymptotic values of the effective stresses at the cavity wall are established. When destructuration is considered, the solution provides lower values of the effective radial stresses near the cavity wall, which are partially compensated by larger values of the excess pore pressures. Parametric analyses and discussion of the influence of soil overconsolidation, initial amount of bonding and rate of destructuration are presented. Finally, the theoretical solution is compared with experimental data of undrained shear strength variation immediately after pile driving in a sensitive clay.