Numerical study on flexural toppling failure of rock slopes using the finite discrete element method

Flexural toppling is a quite complex and common failure mode of anti-dip bedding rock slopes (ABRSs), since it involves not only deformation of the intact rock but also sliding or opening of the joint and fracture of the rock layer. In this work, the finite discrete element method (FDEM) was used to study flexural toppling of ABRSs. The feasibility of FDEM to simulate flexural toppling was firstly verified by a model test. Then, parametric studies were carried out using the FDEM to investigate the influence of the angle of the joint, angle of the slope, and thickness of the rock layer on flexural toppling. Moreover, the failure surface of the slope undergoing flexural toppling was discussed. The results indicate that the failure surface may be a simple plane with an angle to the joint normal ranging from 9 to 23 degrees, or it may be a complex stepped form. The depth of the failure surface gradually increased with the increase in the angle of the rock layer. For less stable slopes against flexural toppling, two failure surfaces were formed within the slope, with the deep failure surface approximately parallel to the shallow one. The failure surface does not necessarily pass through the toe of the slope, but may also be located above it.