Failure Mechanism and Risk Assessment of Multi-Level Cliff in Jiaohua Perilous Rock Mass

Perilous rock mass disasters are typical forms of collapse disasters. Perilous rock masses are widely distributed in mountainous areas around the world and often pose a great threat to residents and line engineering. The correct evaluation of the stability and disaster-causing ability of perilous rock is important for the guarantee of sustainable development for human beings living in mountainous areas. The dynamic disaster effects of perilous rock collapse have always been a hot topic in the field of engineering geological disaster research. This study takes typical #WY8 and #WY47 perilous rock masses in a zone called the Jiaohua rock perilous rock zone in Chongqing, China, as a case study. The Jiaohua perilous rock mass is located in the Kaizhou District of the Three Gorges Reservoir area in China, which is mainly distributed in a ‘long strip’. The initial deformation and collapse of the perilous rock zone occurred in September 2004, and many local collapses have occurred since. In this study, the basic characteristics of the perilous rock belt of Jiaohua rock were first analyzed, and the failure mechanism of the perilous rock mass of Jiaohua rock was then summarized. Then, a numerical model of the perilous rock mass was established by DAN-W, and the disaster process of perilous rock collapse was analyzed. According to the characteristics of perilous rock and cliffs, considering the collapse partition, the collapse path of debris flow can be divided into three sections: the collapse section, slip section, and accumulation section. The calculation results show that the maximum velocity of the front edge of the #WY8 debris flow is 27.26 m/s, the maximum velocity of the trailing edge is 16.71 m/s, the maximum sliding distance is 437 m, and the impact force of the debris flow on the building is up to 52.29 kPa. The maximum velocity of the front edge of the #WY47 debris flow is 31.05 m/s, the maximum velocity of the trailing edge is 21.99 m/s, the maximum sliding distance is 194.31 m, and the impact force of the debris flow on the building is 241.15 kPa. Civil buildings within the scope of collapse are at risk of being completely destroyed. The research results of this study provide a certain theoretical basis for disaster prevention and mitigation work in the hidden danger area of rock avalanche disasters in the Three Gorges Reservoir area.