The shear mechanical behavior of discontinuities under unloading conditions induced by intensive rock mass excavation differs from that under loading conditions. Therefore, the mechanical parameters obtained from the conventional direct shear test cannot effectively be used to assess the stability of excavated rock masses. To solve this problem, we conducted a series of experiments on saw-toothed discontinuities with different undulating angles and initial shear stresses under unloading normal stress with constant shear stress. The test results showed that the shear pattern transformed from cl...
