Abstract: This paper investigates the deformation characteristics and damage mechanism of the lime-treated expansive soil. A series of mechanical property tests under uniaxial compression, one-dimensional consolidation, and triaxial compression are carried out for Jingmen expansive soil. The results show that the lime-treated soil remains fairly stable stiffness and shear strength even after saturated. Under uniaxial compression, whether unsaturated or saturated, the brittle failure occurs for the lime-treated expansive soil, whereas the untreated expansive soil has considerable plastic deformation capacity. On the other hand, under triaxial compression, the lime-treated samples present shear contraction and strain hardening before failure, with the shear dilatancy when the sample was about to failure and strain softening after failure. Moreover, it is observed that the confining pressure had an inhibitory effect on the brittle failure and the shear dilatancy, but even under the confining pressure is 200 kPa, the deformation of the sample is very small at the failure time, which demonstrates the brittle failure. Based on the mechanism analysis, the Duncan model is selected to describe the stress-strain-strength behaviour of the lime-treated expansive soil. The model parameters are calibrated from the aforementioned tests. The comparisons between the parallel tests and predicted results validate the selected model.

Key words: expansive soil, lime-treated, stress-strain-strength behaviour, constitutive modeling, brittle failure, Duncan model