Oral presentation on stress conditions of laboratory shear tests in GESS (Hong Kong)
Published:
Chai S, and Zhao Q. (2023). New insights into stress conditions of laboratory shear tests. The Greater Bay Earth & Environmental Sciences Young Scholars Symposium (GESS) 2023. Hong Kong.
Abstract
Laboratory tests were performed to investigate the shear behavior of rock joints using various experimental setups. The normal and shear stresses on the joints are usually estimated by the average stress, however, the stress distribution during shearing has seldom been specified clearly. Nonuniform stress distribution may result in local stress concentrations and induce local damage, thus influencing the accuracy of estimated shear properties. Therefore, in this study, numerical simulations considering a simple linear velocity weakening law are conducted on smooth rock joints in various laboratory setups to analyze the stress distribution before shear and during stick-slip shear cycles. The results show nonuniform normal and shear stress distribution in almost all the laboratory tests and significant local stress concentration near the edges of the shear surface. The estimated sample-average friction coefficient is slightly higher than the dynamic friction coefficient but lower than the static friction coefficient. Furthermore, a sudden release of the shear stress, especially near the stress-concentrated edges, can be observed in the slip phase during a stick-slip cycle. This study provides a critical review of laboratory shear tests on rock joints and contributes to our understanding of stress distribution and variation during stick-slip shear.
