Risk analysis of progressive cracking and failure of hard rock around deep underground caverns with high sidewall

Abstract

The progressive cracking of hard rock is more significant under the strong unloading effect of excavation of deep buried large caverns, which often leads to the destruction of surrounding rock, the sharp increase of deformation, support damage and other engineering disasters. Relying on a domestic giant underground hydropower station that faces serious aging crack problems of surrounding rock during the excavation period, the risk analysis methods on the progressive cracking and failure of hard rock around deep underground caverns with high sidewall were presented. Firstly, the formation mechanism of cracking and failure risk of hard rock was revealed from the perspective of risk, based on the analysis of the influencing factors of the cracking behaviour. Secondly, the risk consequences and losses caused by progressive cracking of hard rock were summarized through typical historical observation cases. On this basis, the identification and estimation process of progressive cracking and failure risk of hard rock was put forward, according to the characteristics of complex excavation process of the large caverns and the development characteristics of progressive cracking of hard rock. Thirdly, based on the existing risk assessment guidelines for underground engineering, the risk classification principle of progressive cracking of hard rock for large underground cavern was preliminary proposed, including risk occurrence, risk loss and risk grading, and a set of methods for estimating the risk of progressive cracking and failure of hard rock in the underground powerhouse from Baihetan Hydropower Station project was applied to verify the applicability of the method proposed in this paper. This study has important guiding significance for risk assessment of similar disasters and support optimization design of large and deep underground engineering in hard rock.