HYDRAULIC FAILURE MECHANISM OF KARST TUNNEL SURROUNDING ROCK
WANG Jianxiu1，2，FENG Bo2，ZHANG Xingsheng2，TANG Yiqun1，2，YANG Ping1，2
(1. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China；2. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China)
Abstract：According to surrounding rock structure，the hydraulic failure of karst tunnel is divided into the extension of non-transfixion cracks，the extension of transfixion cracks(grouted transfixion cracks)，the rock fall of isolated rock blocks and the collapse of rock wall between tunnel and karst cave. The hydraulic failure mechanisms of non-transfixion cracks and transfixion cracks(grouted transfixion cracks) are analyzed with fracture mechanics method，and the non-transfixion crack is treated as a sheet crack in infinite body. Its extension is calculated with Green and Sneddon¢s solutions，and the transfixion crack is treated as a crack in plate，and its extension is calculated with function of complex variable of Westergaard. The hydraulic failure mechanism of isolated rock blocks is analyzed with stereographic projection and limit equilibrium method，and the calculation formula of limit equilibrium considering water pressure is presented. The hydraulic failure mechanism of rock wall between tunnel and karst cave is analyzed with strength reduction method，and an instance is presented with finite element method. Corresponding control measures are suggested for different failure modes，so as to provide reference to similar projects.
