Experimental and numerical study of the mechanism of block–flexure toppling failure in rock slopes

Block-flexure is the commonest mode of toppling failure and can be frequently encountered in anti-inclined rock slopes. In this work, the failure mechanism of block–flexure toppling (BFT) was investigated using centrifugal and numerical models. The numerical model was configured using the Universal Distinct Element Code (UDEC) and calibrated with the results of the centrifuge test. All the simulation results, including the measured displacements, failure load, and failure surface, are generally in line with that of experimental results. Further, the results of simulations show that, well before the appearance of instability in the jointed rock slope, slipping failure and opening fractures had occurred in the interlayer. Moreover, all the acting points of normal forces in steep joints are located between the bottoms and the midpoints of the columns under consideration, in the process of toppling failure. Finally, sensitivity of joint parameters, including the connectivity rate of discontinuous cross-joints, the thickness of the rock column joint, joint friction angle, and joint cohesion, were performed to investigate the effects of the tensile strength of intact rock. The results indicate that joint cohesion and thickness of the rock column greatly influence the failure load (represents safety factor of the slope). The connectivity rates of the discontinuous cross-joints and joint friction angle were found to have significant effects on the shape and location of the basal failure plane. This research would provide a deep understanding on the failure mechanism of BFT for relevant scholars.