SOIL DISTURBANCE EFFECT ON UNDISTURBED SOFT CLAY UNDER ISOTROPIC AND ANISOTROPIC STRESS CONDITIONS

Abstract

Soil disturbance has been defined as the simultaneous reduction in the peak shear strength and stiffness of undisturbed soft clay (UDS) under cyclic loading, as reported in numerical simulations by previous studies. Furthermore, anisotropy is classified as a dynamic property and strongly influences the mechanical properties of UDS soft clays. A recent study investigated the influence of soil disturbance in both UDS and reconstituted (REC) soft clay; however, the effect of stress-induced anisotropy and its interaction with soil disturbance has not been sufficiently discussed. To address the research gap, the present research aims to provide experimental evidence on the interaction between anisotropy and soil disturbance, which simultaneously act on soft clays under an embankment/structure during cyclic loading. Specifically, this study conducts a series of undrained cyclic triaxial shear tests and post-cyclic monotonic shear tests on UDS specimens under both isotropic (ISC) and anisotropic (ASC) stress conditions to determine the effect of stress-induced anisotropy on soil disturbance. Based on experimental results, the mean effective stress of both specimens under ISC and ASC progressively decreased during cyclic loading; both eventually failed after 1295 and 134 cycles, respectively. The peak shear strength of the specimens under ISC and ASC also decreased by 13% and 43% after 960 cycles and 48 cycles, respectively. It is evident that the specimen under ASC failed during cyclic shearing and exhibited a more pronounced reduction in peak shear strength, despite a significantly shorter cyclic loading history. Therefore, ASC amplifies the effect of soil disturbance on UDS soft clays.