An effective stress-based approach to modeling the chemo-mechanical behavior of saturated active clay

Pore water chemistry can exert significant controls over the chemo-mechanical behavior of chemically-active soils, which has not been characterized by using the traditional Terzaghi’s effective stress to a satisfactory extent. In this paper, based on the concept of intergranular stress, the effective stress for saturated active soils is first reconceptualized and then incorporated into the framework of the modified Cam-Clay model to describe the mechanical response of soils upon complex chemical and mechanical loadings. The proposed model is capable of capturing very well the diverse features of the chemo-behavior of saturated active soils, while inheriting all the advantages of the MCC model, by introducing only one additional parameter. Within this context, a simple equation is derived to predict the development of swelling pressure with the variation of pore water chemistry. It is shown the proposed swelling-pressure equation predicts very well the development of swelling pressure for expansive soils with a dilute pore solution, though discrepancy appears at high concentration. Because the double layer of clay particles is severely suppressed at high salt concentration, the microfabric of soil can be significantly changed, pointing to the importance of taking into account the effect of soil fabric in the constitutive modeling of active soils with high pore water concentration.