Minimum safe thickness of rock plug in karst tunnel according to upper bound theorem

作     者：YANG Zi-han ZHANG Jia-hua 杨子汉;张佳华

作者机构：School of Civil Engineering Central South University Changsha 410075 China 

出 版 物：《Journal of Central South University》 (中南大学学报（英文版）)

年 卷 期：2016年第23卷第9期

页      面：2346-2353页

核心收录：

学科分类：081406[工学-桥梁与隧道工程] 08[工学] 0814[工学-土木工程] 082301[工学-道路与铁道工程] 0823[工学-交通运输工程] 

基　　金：Project(2013CB036004)supported by the National Basic Research Program of China Project(51378510)supported by the National Natural Science Foundation of China Project(CX2014B069)supported by Hunan Provincial Innovation Foundation for Postgraduate,China 

主　　题：karst tunnels rock plug minimum safe thickness upper limit theorem failure mode 

摘      要：High pressure and water-bearing caverns ahead of a karst tunnel face tend to cause geological disasters, such as water and mud bursts. So, the determination of safe thickness of the reserved rock plug is a key technical problem to be solved for karst tunnel construction. Based on the Hoek-Brown nonlinear failure criterion, the minimum safe thickness of rock plug was investigated in the light of the limit analysis theory. On the basis of the proposed failure mode, the expression of the minimum thickness for rock plug was obtained by means of upper bound theorem in combination with variational principle. The calculation results show the influence of each parameter on safe thickness and reveal the damage range of rock plug. The proposed method is verified by comparing the results with those of the drain cavern of Maluqing Tunnel. The research shows that with the increase of compressive strength and tensile strength as well as constant A of Hoek-Brown criterion, the safe thickness decreases, whereas with the increase of cavern pressure, tunnel diameter, and constant B from Hoek-Brown criterion, the safe thickness increases. Besides, the tensile strength, or constants A and B affect the shear failure angle of rock plug structure, but other parameters do not. In conclusion, the proposed method can predict the minimum safe thickness of rock plug, and is useful for water burst study and prevention measures of tunnels constructed in high-risk karst regions.