Uniaxial compressive study on mechanical properties of rock mass considering joint spacing and connectivity rate

Abstract

To explore the effect of joint spacing and joint connectivity rate on the uniaxial compressive strength (UCS) and elastic modulus of jointed rock mass, compression tests on preset intermittent fractured specimens were performed. Test results show that the anisotropy of UCS of jointed rock mass tends to increase with joint connectivity rate. The decreasing rates of UCS and elastic modulus of jointed rock mass, when the loading direction is perpendicular to the joint plane, are higher than those when the loading direction is parallel to the joint plane with respect to joint connectivity rate and jointing index (the ratio of the length of jointed rock mass specimen to the joint spacing). The fourth-degree polynomial function proposed in this study is appropriate to analyze the nonlinear variation law of equivalent peak UCS of jointed rock mass with joint connectivity rate. The power function proposed in this study is suitable to describe the nonlinear variation law of equivalent peak UCS and equivalent elastic modulus of jointed rock mass with jointing index. However, the number of times and the number of parameters of multiple polynomial function and the number of power function need to be determined according to site-specific test results of practical project.