Shear behaviors of clay-infilled joint with different water contents: experiment and model

To better understand the effect of water content on shear behaviors of clay-infilled joint, a series of direct shear experiments were performed on clay-infilled joints prepared by reproducing the standard JRC profiles on a rock-like material and placing the clay infill with various water content inside the joint, and a shear strength model of infilled joints was established. For most of the clay-infilled joints, the shear stress versus shear displacement curve is characterized by gentle type; i.e., the residual shear stress value is close to the peak value, with the absence of a softening phase on the curve. There is a trend to negative correlation between the shear strength of clay-infilled joints and the t/a ratio when t/a is smaller than a critical value ( t/a ) cr . Shear strength of clay-infilled joints decreases with an increase in water content, if water content is below liquid limit of clay infill; however, the shear strength of infilled joint with liquid clay is higher than that of the infilled joint with plastic clay. Based on the JRC-JCS strength criterion, a revised shear strength model of infilled joint is proposed, by the proposed negative exponential equation between friction angle and t/a ratio. The good agreement between experimental results and predictions indicated that the revised shear strength model is capable of estimating the peak shear strength of infilled rock joints.