A constitutive model of compacted bentonite under coupled chemo-hydro-mechanical conditions based on the framework of the BExM

Abstract

A coupled chemo-hydro-mechanical model for compacted bentonite based on the Barcelona expansive model (BExM) that distinguishes between the microstructure and macrostructure was developed in this work. The effective stress principle was modified by introducing the osmotic stress pπ, which is considered to govern the elastic strain of the compacted bentonite. The yield functions were deduced, and the yield surface was depicted in the smatric-pπ-pnet space. Validation of the proposed model was conducted by simulating a series of wetting–drying tests on compacted bentonite under different net vertical stress and osmotic stress conditions and by salinization-desalinization tests on compacted bentonite at different vertical stresses. A comparison between the predicted and measured volumetric strains in different wetting–drying and salinization-desalinization cycles proves the potential of the model to capture the main features of the volume change behavior in response to coupled chemo-hydro-mechanical processes. The results also indicate that the micro–macro coupling functions are not only dependent on the net vertical stress but are also associated with chemical effects. A conceptual method to incorporate chemical hardening and chemical softening mechanisms into the micro–macro coupling functions was then developed.