Closed-Form Solution for Cavity Expansion in Strain-Softening and Undrained Soil Mass Based on the Unified Strength Failure Criterion

Abstract

This paper presents a solution for cavity expansion in strain-softening and undrained soil mass based on the unified strength failure criterion. Stress distribution around the cavity expansion was divided into three regions (i.e., elastic, softening, and plastic flow zones). The deformation was assumed to be governed by the small strain in the elastic zone and the large strain in the softening and plastic flow zones, and a closed-form solution of the stress and strain was obtained for the different zones. Moreover, the softening zone radius, the excess pore-water pressure in the plastic flow zone, and the ultimate cavity expansion pressure were obtained for cavity expansion in the strain-softening soil mass by incorporating certain factors, such as large strain, drainage condition-, and intermediate principal stress. Furthermore, several cases were analyzed using the proposed approach. The results of the ultimate cavity expansion pressure (e.g., k = 1) were consistent with those obtained through previous theories and local tests.