Research on strength behavior of rock mass containing discontinuous joints by direct shear test under different joint surface morphologies

By direct shear test, strength behavior of rock mass containing discontinuous joints with different joint surface morphologies is researched. The extension process to the rock mass can be divided into 4 stages: before initial cracking stage, crack stable growth stage, unsteady growth stage and friction stage. According to the experimental phenomena and the shear deformation curve, initial cracking strength, critical strength, failure strength and residual strength are researched. With the same normal stress, the joint surface morphology is rougher, not only the failure strength is higher, but also the initial cracking strength, critical strength, and residual strength are higher. With different joint surface morphologies, the ratio of the initial cracking strength and failure strength is about 70%; the ratio of the critical strength and failure strength is about 90%; but the ratio of t initial cracking strength and failure strength is not stable, which is about 50%- 90%. The experimental verification is provided to further study failure theory of rock mass containing discontinuous joints.