Strength Deterioration Mechanism of a Typical Soft and Hard Interbedded Rock Mass in Three Gorges Reservoir Area Under Wetting and Drying Cycling Condition
Qiong WU1#+, Di WANG1, Huiming TANG1, Jintao KANG2, Zhen MENG1, Xiaoxue HUO1, Yuxin LIU1, Shiyu LI1
1Faculty of Engineering, China University of Geosciences, Wuhan, China, 2School of Qilu Transportation, Shandong University, Jinan, China

Due to cyclic reservoir water level fluctuations, rock mass in hydro-fluctuation belt of reservoir bank are subjected to wetting and drying cycles, which is detrimental to the stability of bank slope. In this study, the strength deterioration mechanism of soft and hard interbedded rock mass under wetting and drying cycling condition are investigated by taking a typical sliding-prone rock mass with silty mudstone and argillaceous siltstone interbedded of the Badong formation in the Three Gorges Reservoir as the research object. The degradation equations of strength parameters of silty mudstone, argillaceous siltstone and bedding planes between these two rock types under wetting and drying cycling conditions are firstly established through a series of laboratory experiments. Based on these obtained degradation equations, uniaxial/triaxial compression numerical experiments were then carried out to study the contribution of strength degradations of rocks and bedding plane to the compressive strength degradation of soft and hard interbedded rock masses and its relationship with the dip angle and confining pressure. The results indicate that the influence of strength degradation of rocks and bedding planes on the compressive strength degradation of soft and hard interbedded rock masses are obviously varied with dip angle, which can be divided into range of controlling by soft rock, range of controlling by combination of soft rock-hard rock-bedding plane, range of controlling by bedding plane and range of controlling by hard rock. The influence of confining pressure on the contribution of strength degradations of rocks and bedding plane on compression strength degradation of soft and hard interbedded rock mass varies with the dip angle, while the confining pressures in a relatively low level used in this study have little impact on the limits of dip angle partitions by deterioration mechanism. Based on the data acquired from the numerical experiments, the equation to estimate the compression strength of the typical soft and hard interbedded rock mass of the Badong formation under wetting and drying cycling condition was developed.