Stability of bolt-supported concealed bedding rock slopes with respect to bi-planar failure

Bi-planar failure is one of the most common issues encountered in concealed bedding rock slopes (CBRSs). Fully grouted bolts are widely adopted to improve the stability of slopes and prevent failure due to their high efficacy and low cost. In this study, a bi-planar mechanical model is first established for the sliding body based on the interactions between active and passive blocks. The supporting forces supplied by fully grouted bolts are then introduced and limit equilibrium theory is used to analyze the stability of the bolted CBRSs. A parametric analysis is conducted to investigate the effects of varying the bolt angle (angle of the bolt with respect to the joint plane), bolt diameter, and bolt location on the stability of the CBRSs. Finally, comparisons are made between results obtained using the proposed method of analysis and discrete element modeling. The results obtained using the two different approaches are in good agreement. There is an optimal bolt angle that maximizes the stability of the bolted CBRSs–its value is approximately equal to the friction angle of the joint. The slope stability (and contribution made by the bolts) also increases with the diameter of the bolts used, the variation increasing according to a power function. The proposed method of analysis offers a sound basis for better understanding the mechanism by which fully grouted bolts reinforce such slopes and can be used as a useful design aid for protecting CBRSs against bi-planar failure.