Nonlinear constitutive model of soil–bentonite based on triaxial tests along different stress paths

Abstract

To investigate the constitutive behavior of soil–bentonite, which is commonly used as backfill for cutoff walls, a series of triaxial tests was conducted along different stress paths. The tested soil–bentonite comprises 5% Wyoming bentonite and 95% silty clay excavated from a landfill site located in Jiangsu Province, China. Some mechanical properties of the soil–bentonite, including the compression characteristic, shearing characteristic, and coupled deformation of mean and deviatoric stress, were examined based on the test data. Then, a nonlinear constitutive model was developed under the axisymmetric condition based on a modified hypoelastic model framework. All six independent parameters included in the model were calibrated according to the test data. The mechanical behaviors that the triaxial tests revealed can be fully reflected by the nonlinear model; therefore, it can reasonably describe the stress–strain behaviors of the soil–bentonite in triaxial tests of this study and other literature. Compared with the Modified Cam-Clay model, the prediction effect for the shear strain of the nonlinear model is better. According to a large-scale in situ test employing a soil–bentonite cutoff wall, the actual stress paths of soil–bentonite are basically included in the application scope of the nonlinear model, preliminarily indicating its applicability for practical engineering projects.