A Method for Evaluating the Maximum Bending Degree of Flexural Toppling Rock Masses Based on the Rock Tensile Strain-Softening Model

Abstract

Flexural toppling occurs when a series of layered rock masses bend towards their free face. It is important to evaluate the maximum bending degree and the requirement of supports of flexural toppling rock mass to prevent rock mass cracking and even failure leading to a landslide. Based on the rock tensile strain-softening model, this study proposes a method for calculating the maximum curvature (C_ppmax) of flexural toppling rock masses. By applying this method to calculate C_ppmax of 9 types of rock masses with different hardness and rock layer thickness, some conclusions are drawn: (1) the internal key factors affecting C_ppmax are E^⋆ (E^⋆= E_ss/E₀, where E₀ and E_ss are the mean deformation moduli of the rock before and after reaching its peak tensile strength, respectively), the strain ε_t corresponding to the tensile strength of rock, and the thickness (h) of rock layers; (2) hard rock layers are more likely to develop into block toppling than soft rock layers; and (3) thin rock layers are more likely to remain in flexural toppling state than thick rock layers. In addition, it is found that C_ppmax for flexural toppling rock masses composed of bedded rocks such as gneiss is related to the tensile direction.