Effect of the number of coplanar rock bridges on the shear strength and stability of slopes with the same discontinuity persistence

Analyzing the shear resistance of a potential sliding surface based on discontinuity persistence usually does not consider the number of coplanar rock bridges. To examine the effect of the dispersion/number of rock bridges on the shear strength and rock slope stability, direct shear tests and large-scale rockslide simulations were conducted employing the 2D particle flow code (PFC2D). The shear strength of rock bridges under different configurations and the same discontinuity persistence was analyzed based on both the shear behavior controlled by the stress response and crack propagation. The results at both the laboratory and slope scales indicate that the shear resistance decreases with increasing dispersion/number of rock bridges due to multiple rock bridges breaking separately, the mechanism of which is that the rock bridge system more easily experiences initial failure with increasing dispersion/number of rock bridges. On this basis, a function of the strength reduction coefficient with the number of rock bridges was established considering the laboratory-scale numerical simulation results. A feasible stability analysis method, i.e., the improved limit equilibrium method based on the strength reduction coefficient, was proposed to consider the effect of the dispersion/number of rock bridges on the slope stability, which is a useful innovation to ensure that the stability analysis method of potential rockslides, including coplanar rock bridges, is more realistic and accurate.