Scale Effect on Shear Strength of Computer-Aided-Manufactured Joints

Abstract

In order to systematically study the scale effect on the shear strength of rock joints, this study used the computer-aided-manufacturing system to reproduce the artificial rock joints for Barton's standard joint profiles of JRC=4~6 and 18~20, natural rock joint profiles, and saw-toothed joints. We divided, enlarged, reduced, and assembled these joint profiles to obtain joint specimens of various sizes ranging from 75 mm to 300 mm in length. Direct shear tests were conducted on these joint specimens to obtain the peak shear strengths under different normal stresses. The surface conditions of the joints at failure were also examined. Based on the test results in this study, it was found that the joint surface geometry configuration rather than the specimen size itself is the main factor in the scale effect on the peak shear strength of rock joints. The geometry configuration or roughness of each individual joint should be evaluated in the use of empirical relations to compute the shear strengths of rock joints of various sizes.