Mechanism and Structural Evidence of Interlayered Rock Slope Failures

The stability of a series of competent and incompetent lithologies is very hard to assess kinematically as well as analytically, as both soil and rock materials are involved. Therefore, in alternate series of competent and incompetent rock units, the overhangs of competent rocks are the most striking problematic features that mainly occur in sedimentary rocks. Given the present understanding, the slopes in such rocks given discontinuity orientations are routinely considered stable kinematically, but still, experience massive rock falls. Regardless of the analyses, as a rule of thumb, horizontal to sub-horizontal discontinuities and discontinuities dipping moderately steep to steep into the slope are considered favorable to stability. However, this rule holds good for the same geological domain with the same lithology. Despite the extensive studies of differential weathering for competent and incompetent rock units in the line of material properties such as durability, there was hardly any effort to limit the likelihood of this phenomenon through kinematic analyses upfront that can provide the basis for detailed investigations for a particular case. This research discusses the mechanism and structural evidence of undercutting-induced rock slope failures. A preliminary kinematic criterion for interlayered rock slope failure is proposed based on field evidence, physical modeling, and DEM simulations. This study also recommends prospects to carry out further studies. The proposed criterion basically provides upfront the likelihood of rock falls that are routinely missed using the already developed criteria for various modes of rock slope failure.