Effect of the joint roughness coefficient on the strength for rocks with a through-going joint

The strength of jointed rock often exhibits significant directionality, which is crucial for ensuring the stability of jointed rock engineering. Given that laboratory-measured strength values of jointed rock tend to be discrete and non-repeatable, this study digitized ten standard joint roughness profiles to establish a numerical model characterizing the strength and deformation behavior of jointed rock. The relationship between uniaxial compressive strength and the joint roughness coefficient (JRC) was analyzed for rocks with a joint dip angle of 15° and continuous joint persistence. Experimental results demonstrate the following: (1) Under uniaxial compression, the uniaxial compressive strength and joint surface wear rate are not monotonically increasing functions of JRC. The minimum strength and maximum wear rate both occur at JRC values of 6–8. (2) Under axial stress, relative sliding between the upper and lower blocks of the joint induces stress concentration near the joint and adjacent areas; however, the number of cracks does not exhibit a positive correlation with JRC. (3) The peak stress of the rock primarily depends on the development of shear cracks and wing cracks along the joint. The maximum number of wing cracks at peak stress is observed when JRC ranges from 6 to 8. The study concludes that effectively inhibiting the initiation and propagation of shear cracks and vertically oriented wing cracks along joint surfaces can provide a theoretical foundation for the development of stability control strategies for ore pillars.