Effect of torsional shear stress on the deformation characteristics of clay under traffic load

The soft clay under the road ground will suffer cyclic torsional shear stress encountered traffic load in addition to axial stress, which will cause further deformation of clay. To investigate the effect of torsional shear stress on the cumulative axial strain of clay, a series of undrained tests under cardioid stress path were performed on K₀ consolidated undisturbed samples by using a hollow cylinder apparatus (HCA). The effect of vertical cyclic stress ratio (VCSR) and shear stress ratio (η) on the deformation and degradation characteristics of clay was investigated. The results indicate that there is inconsistency between the strain path and stress path. The increase in η further accelerates the accumulation of axial strain, which resulted from the degradation of clay induced by torsional shear stress. Considering the VCSR and η, a calculation method of degradation index was developed. Furthermore, a cumulative axial strain prediction model of clay under the cardioid stress path was established considering the degradation. This model addresses the limitation of traditional prediction models by considering the impact of torsional shear stress on cumulative axial strain.