A numerical investigation on undrained expansion of a cylindrical cavity under biaxial in situ stresses using anisotropic S‐CLAY1 model

Abstract

Cavity expansion under biaxial in situ stresses is commonly encountered in geotechnical engineering, which, however, has not been well-investigated at present. This paper numerically investigates the undrained expansion responses of a cylindrical cavity in S-CLAY1 soil under biaxial in situ stresses. The advanced anisotropic S-CLAY1 model is integrated by the semi-implicit scheme and implemented as a user-defined subroutine (UMAT) in the finite element model (FEM) to represent the elastoplastic behavior of the soil around the cavity during expansion. To validate and calibrate the FEM, a benchmark solution for cavity expansion under uniform in situ stress is specifically developed and compared with the FEM. Parametric studies are performed based on the FEM to numerically investigate the salient expansion responses under biaxial in situ stresses. The results reveal that the expansion responses, including the expansion pressures, the excess pore water pressures at the cavity wall, the distributions of the stress components around the cavity, are not only remarkably different with those under uniform in situ stress, but also different with the findings from the approximate analytical solutions. What is particularly surprising is that the positions of the maximum and minimum expansion pressures reverse with expansion of the cavity. The outcomes of present study reveal the significant mechanisms of undrained expansion of a cylindrical cavity under biaxial in situ stresses.