New failure criterion for rock slopes with intermittent joints based on energy mutation

Step-path failure is a typical unstable mode of rock slopes with intermittent joints, and the accurate prediction of their stability is of great significance. In the present study, an energy calculation programme for the slope system based on secondary development of two-dimensional particle flow code (PFC2D) was proposed. The step-path failure modes of slopes with intermittent joints were well reproduced and could be classified into three types according to the penetration modes of rock bridges: shear penetration, tensile penetration, and tensile–shear mixed penetration. The evolution of gravitational potential energy, elastic strain energy, and kinetic energy were also captured. Based on this, the failure criterion depending on the energy mutation was established. When the slope approached the critical instability state, the gravitational potential energy reduction, kinetic energy increment, and dissipative energy increment all increased suddenly, while the elastic strain energy increment suddenly decreased, indicating that the energy mutation could be used as the failure criterion for rock slopes with intermittent joints. The proposed energy mutation criterion has the advantages of clear physical meaning, strong integrity, easy judgement, and good applicability, which provides certain theoretical support for evaluation of rock mass stability and prediction of instability of jointed slopes.