Stability analysis and design charts for over-dip rock slope against bi-planar sliding

Bi-planar sliding is one of the main instabilities in over dip rock slope. The geometry and strength of the bi-planar sliding surface comprised of two sets of cross-discontinuities play an important role in slope stability assessment. However, few studies had been conducted to systematically investigate the influences of them. In this study, three categories of failure modes related to the failure region, namely, the shallow, intermediate and deep, are proposed. Corrected Implicit Transfer Coefficient Method (CITCM) with the modified sliding surface is proposed as an alternative to the Limited Equilibrium Method (LEM) for calculating the slope factor of safety (Fos). The change patterns of slope stability are derived from the Fos values calculated via CITCM considering different scenarios of geometrical and mechanical parameters of the critical bi-planar sliding surface. The equivalent slope model for the overlap rock slope under bi-planar sliding is proposed to explain slope stability change patterns reasonably. The design charts for preliminary slope stability assessment are presented in the over-dip rock against bi-planar sliding. Finally, compared with other traditional Limited Equilibrium (LE) approaches, case history engineering applications validate the proposed design charts in calculating Fos, determining the critical sliding surface, and recognizing the failure mode is more effectively.