Physical Model Tests on the Effect of Anchoring on the Splitting Failure of Deep Large-Scale Underground Rock Cavern

A set of splitting cracks often occur in the high side wall of the deep underground hydropower station due to the excavation-induced unloading during the construction period, which causes great risk to the safety of the cavern. In this paper, taking the Pubugou Hydropower Station as the engineering background, we perform true three-dimensional geomechanical model tests to investigate the effect of anchoring on restraining splitting failure. The evolutions of deformation and stress in the surrounding rock and the internal force of support structure are monitored. The test results of unsupported model reveal that the displacement and stress of the surrounding rock at the side wall and haunch show non-monotonic fluctuations after excavation. In the supported model, no splitting failure occurs and the displacement is much smaller compared with the unsupported model. During the layered excavation of the high side wall cavern, the stress concentration area moves to the bottom of the cavern in the supported model. After excavation, the displacement and radial stress present a monotonous change in the supported model, but within the range of 1.5 times cavern span, the tangential stress presents a fluctuating variation that first increases and then decreases. It can be seen that the anchorage support can effectively limit the splitting failure and improve the distribution of stress in the surrounding rock. These results provide basis and reference for in-depth analysis of the excavation stability of high-side wall caverns under high ground stress and optimization of the cavern support design.