Critical shear strain and sliding potential of rock joint under cyclic loading

A new concept of critical shear strain (epsilon(tau critical)) of rock joint under cyclic loading is presented, and the role of epsilon(tau critical) in evaluating the sliding potential of rock joint is highlighted. A series of cyclic triaxial tests was conducted on a cylindrical rock joint specimen with a replicated rough surface representing a joint roughness coefficient (JRC) value of 12.6 oriented at 60 degrees with respect to the horizontal plane. The experimental results indicate that the onset of instability of rock joint is suppressed with increase in confining pressure and number of loading cycles (N) until the normalized shear deformation increases beyond a threshold value of epsilon(tau critical). Generally, the critical strain of most rock types is considered in the proximity of 1% under small strain conditions [36-37], however, in this study, the critical strain concept is extended to the domain of rock joints, and a semiempirical model to more rigorously quantify the critical shear strain (epsilon(tau critical)) of rock joint is suggested considering the effect of joint roughness coefficient (JRC), cyclic loading amplitude, and the number of loading cycles (N). Also, a rational classification of Joint Sliding Potential (JSP) based on the epsilon(tau critical) and normalized total shear strain (epsilon(theta N)) of rock joint is proposed to characterize the cyclic loading induced sliding instability of a rock discontinuity.

Automated summary

This paper introduces a new concept of critical shear strain of rock joint under cyclic loading and emphasizes its role in evaluating the sliding potential of rock joint. A series of cyclic triaxial tests were conducted on a cylindrical rock joint specimen, and experimental results indicate that the onset of instability of rock joint is suppressed beyond a threshold value of critical shear strain. The critical strain concept is extended to rock joints and a semiempirical model is suggested to quantify the critical shear strain, considering the effect of joint roughness coefficient, cyclic loading amplitude, and the number of loading cycles. Additionally, a rational classification of Joint Sliding Potential based on critical shear strain and normalized total shear strain is proposed to characterize the cyclic loading induced sliding instability of a rock discontinuity.