Experimental investigation on splitting failure of high sidewall cavern under three-dimensional high in-situ stress

Abstract

In strata under high in-situ stress, engineering disasters often occur in high sidewalls of underground powerhouses due to excavation-induced unloading, which produces many adverse effects to the construction of the cavern. True three-dimensional (3D) geomechanical model tests were conducted to investigate the splitting failure of high sidewall rock caverns under high in-situ stress. Taking the main powerhouse of Pubugou Hydropower Station as a case study, and based on a self-developed 3D loading system and an analogous material, we reproduced the splitting failure of high sidewall cavern under high ground stress. Using various measuring methods, we obtained the stress and displacement of the surrounding rock considering the construction process and spatial distributions. The results showed that the excavation-induced unloading led to fractures in the sidewall, and a new stress field was generated in the surrounding rock. After superposition with the original stress field, the rock mass could rupture again, forming new rupture and intact zones. The model test results effectively revealed the formation conditions and failure characteristics of splitting failure of rock caverns with high sidewalls. Moreover, they could provide reliable bases for further studies on the formation mechanism of splitting failure of high sidewall caverns under high in-situ stress.