A Semi-Empirical Shear Strength Model for Infilled Rock Fractures with Infills in an Unsaturated State

Based on the results of recent studies, comprehensive characterization of the behavior of infilled rock fractures under saturated and unsaturated conditions requires knowledge of morphological details of fracture surface, as well as state of stress of infill materials and their initial innate conditions (e.g., void ratio, water content, degree of saturation and dry density). This paper describes a semi-empirical equation to interpret the effects of wall-roughed nature of the fractures and presence of partially saturated fine materials within the fractures on the behavior of infilled rock fractures during shear. The proposed equation incorporates the soil-water retention curve parameters as well as hardening due to changes in either volume or degree of saturation into existing models originally developed for fractures with saturated infills. The literature data is also used to evaluate the reliability of the proposed equation in predicting the shear strength of infilled rock fractures in unsaturated conditions.