Study on shear strength of expansive soil considered softening and slope stability analysis with FLAC3D

Swell-shrinkage, crack growth and over-consolidation are the main characteristics of expansive soil, and it is an over-consolidation soil undergone drying-wetting cycles. So there may be some faults to analyze expansive soil slope stability adopting the traditional strength criterion and calculation methods. In this paper, triaxial tests were carried out to obtain the relations between the parameters of shear strength and generalized plastic shear strain firstly. The soil shear strength increases and then decreases along with the increasing of shear deformation due to soil over-consolidation, and the residual strength is achieved. The functions are applied in simulating the relations between the parameters and generalized plastic shear strain in order to analyze expansive soil slope stability. Then the Strain Hardening Softening (SHS) model in FLAC(3D) was adopted to analyze the slope stability combined with strength reduction method. Results showed that the SHS model could be used to analyze the expansive soil slope stability considered soil softening. The concentrated area of plastic shear strain expanded gradually from the slope base and top to the middle of slope and was linked totally. The results were indicated that the soil characteristics of softening should be considered in analysis on expansive soil slope stability and the judgment of generalized plastic shear strain for expansive slope stability by FLAC(3D) is feasible.