Mechanisms of failure in in-situ rock shear tests under low normal stress

Abstract

The mechanisms of in-situ rock shear tests were investigated for the sake of constructing a theoretical method for the estimation of the strength of rock masses. Localized failure in the testing process was especially noticed, and it was treated with Mohr's failure criterion. The investigation consisted of experiments on gypsum models whose conditions were similar to those in in-situ rock shear tests and of stress analyses for these experiments. Theoretical interpretations of the characteristic cracking process and of the mechanisms of the appearance of shear strength, measured by in-situ rock shear tests under relatively low normal stress with the uniaxial compressive strength, were obtained from the results. No macroscopic discontinuity was considered for the sake of the resolution of the fundamental characteristics of the testing method.