Potential failure mechanism of a rock slope with weak intercalated layer and the reinforcement effect evaluation

Rock slopes with weak intercalated layer are prone to slide because of engineering disturbance or water intrusion deterioration, which poses severe threats to human life and property safety. Identifying the water-induced deterioration characteristics of such interfaces, as well as the potential failure mechanism of such slope is of great importance for scientific prevention. The right abutment slope of Gushan Reservoir is composed of thick quartz sandstone and thin argillaceous shale interlayer inclined downstream, dip angle of about 10°. Besides, relief joints with a steep tendency to the valley at the top of the slope were found. Once the shear strength of the shale decreases due to the reservoir impoundment, the slope might slide, threatening the safety of the dam. For this reason, basic data of the slope were presented by field geological and UAV aerial survey. Then, the strength deterioration law of shale induced by water was revealed by large in-situ direct shear tests. Finally, the potential failure mechanism of the slope under different conditions, as well as the feasibility of the proposed reinforcement scheme were analyzed utilizing three-dimensional numerical simulation. The results showed that the shear strength of the saturated shale was about 50% of that under natural state. The stability of the slope would decrease due to the strength deterioration of the weak interlayer, and the sliding along the weak layer might occur, resulting in local deformation at the right end of the dam. Concrete plugs to be arranged along the potential sliding surface was an effective reinforcement measure for such slope. These results might provide a reference for the stability evaluation and reinforcement design of similar slopes.