Physicochemical effect on shear strength characteristics of clayey soils based on ring-shear experiment

Pore fluid chemistry can significantly influence the shear strength characteristics of a clayey soil. To explore the underlying mechanisms, a series of ring shear experiments are performed on two natural clays, which represent two typical types of clayey minerals, i.e., expansive montmorillonitic clay and low-plasticity kaolinitic clay. The effects of pore solution concentrations on the shear strength of the two clays are experimentally characterized. It is shown that the shear strength of the expansive clay can be significantly influenced by the pore solution chemistry, whereas that of the low-plasticity clay proves to be relatively insensitive to it. To capture the main features of the shear strength behavior of clayey soils, the concept of intergranular stress, which is an extension of the Terzaghi’s effective stress to incorporate physicochemical effect, is introduced to interpret the experimental data. It is found that the evolution of residual shear strength can be very well characterized by using the intergranular stress, showing that the proposed intergranular stress formulation can be used alternatively to describe the stress state of clayey soils saturated with various pore solutions.