Mechanical behavior and constitutive modelling of expansive soils under conditions of wetting and low confining stress

Typical deformation and failure of expansive soils usually occur under conditions of wetting and low confining stress. However, the mechanisms of coupling between mechanical and hydrological behaviors under those conditions are still obscure. Therefore, the soil water retention, volume change and strength behavior of expansive soils are investigated through systematically designed suction-controlled hydro-mechanical coupled tests under varying saturation conditions along wetting path. The test program involves with the instruments including the double-cell unsaturated soil triaxial test system and the Fredlund soil water characteristic devices. The tests last almost 800 days, and the soil water retention, volume change, and strength behavior of Jingmen medium swelling soil under conditions of wetting and low confining stress are acquired. The Barcelona basic model is used to describe the unsaturated stress-strain-strength behavior under those conditions. The van Genuchten model is used to describe the unsaturated seepage process. Combined with the other test results of the soil over the past 10 years, the complete 13 BBM parameters and VG model parameters of Jingmen medium swelling soil under those conditions are calibrated. The constitutive modelling shows that the above models and parameters can reproduce the mechanical behavior of the soil under conditions of wetting and low confining stress effectively. The aim of this study is to improve the prediction capability of the related expansive soil problems, e.g., rainfall-induced landslides and deformations of pavement.