Empirical formula of shear strength for double structural plane based on joint roughness coefficient
FAN Xiang1，2，3，DENG Zhiying1，AN Honglei1，WU Rui1，REN Xianda1，DING Fan1
(1. School of Highway，Chang?an University，Xi?an，Shaanxi 710064，China；2. Hunan Province Key Laboratory of Safe Mining Techniques of Coal Mines，Hunan University of Science and Technology，Xiangtan，Hunan 411201，China；
3. CCCC First Highway Consultants Co. Ltd.，Xi?an，Shaanxi 710075，China)
Abstract：To reveal the shear strength difference of direct shear and bi-direct shear of structural plane and better evaluate the stability of layered rock mass，four Barton standard profile lines were selected to establish the structural plane models，and the rock-like samples containing one or two structural planes were made for shear tests. Based on the experimental results，the differences of peak shear strength( ) between single and double structural planes under three normal stresses( ) as well as the reasons for them were analyzed quantitatively. Based on the particle flow simulation results，the empirical formula of the peak shear strength for the double structural plane with the same JRC value was derived firstly. Then，the combined joint roughness coefficient ( ) was introduced to characterize the roughness of double structural plane with different JRC values. After the relevance between low roughness coefficient( )，high roughness coefficient( ) and was found，an empirical formula of the double structural plane with different JRC values considering the effect of and to peak shear strength was established. Eventually，an empirical formula of the peak shear strength for double structural plane with any combination of JRC values was established via a comprehensive analysis of the evolution of peak shear strength with the mixed joint roughness coefficient. During the process that the growth trend of -JRC curve increases with the increase of ，the peak shear strength of double structural plane increases with the sum of JRC value when is constant. Importantly，when the sum of JRC value is small，the peak shear strength of double structural plane with different JRC values is controlled by the side of lower JRC. However，the control effect decreases with the increase of the sum of JRC value，and thus the peak shear strength is gradually controlled by the side of higher JRC.
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2023, Vol. 42 
