Limit state analysis of stepped sliding of jointed rock slope based on tensile-shear composite failure mode of rock bridges

Jointed rock landslides with stepped sliding surfaces are common in practical engineering. At present, the mechanical mechanism for the formation of a stepped sliding surface based on the tensile-shear composite failure mode of rock bridges is not clear. In addition, considering the development of secondary joints, the strength parameters of the rock bridges and joint surfaces with different weakening coefficients Kc (cohesion weakening coefficient) and Kφ (friction coefficient (tanφ) weakening coefficient) are more realistic and reliable. Based on this, considering these different weakening coefficients, a limit state analysis model of jointed rock slope stability with a stepped sliding surface based on tensile failure and tensile-shear composite failure modes of rock bridges is constructed. The influences of key parameters on the slope stability are investigated. The results show that the existence and different failure modes of rock bridges have significant influences on the slope stability. The dimensionless parameter u (reflecting the contribution of the tensile strength of rocks), Kc, and rock bridge angle β3 have significant influences on the jointed rock slope stability. When β3 is a large value, u has a significant influence on Fs. Fs decreases nonlinearly with an increase in Kc and increases linearly with an increase in Kφ. Under the tensile-shear composite failure mode, when tensile force is dominant, Fs relatively increases; when shear force is dominant, Fs relatively decreases. Therefore, the inconsistency of the changing trend of Fs caused by the tensile failure of rock bridges is solved by determining the tensile-shear composite failure mode.