蛇蟠岛清风洞古采石场中某组结构面长期抗剪强度的反分析

Back analysis of long-term shear strength of structural plane group in Qingfeng Ancient Quarry of Shepan Island

以位于浙江省三门县蛇蟠岛清风洞古代凝灰岩采石场中的某组结构面(编号分别为J1～J4)为研究对象,利用反分析方法得到了结构面的长期抗剪强度参数:凝聚力c=0.078 MPa,内摩擦角φ=15.76°。反分析的具体步骤如下:①假设结构面J1～J4符合摩尔-库仑准则,且岩石为均质弹性和各向同性的;②根据结构面处于极限平衡状态(即稳定性系数k=1),列出以参数c、φ为未知数的极限平衡方程;③利用FLAC3D进行三维数值计算,并从计算结果中提取求解极限平衡方程所需的数据,并将数据代入上述方程便可得到4个二元一次方程;④求解此矛盾方程组即可得结构面的长期抗剪强度参数c、φ值。

Based on the structural plane group （a total of four, named J1 -J4） in Qingfeng Ancient Quarry located in Shepan Island of Zhejiang Province of China, the values of long-term shear strength parameters, cohesion and internal frictional angle, of the corresponding structural planes of the tuff were carded out using back analysis method. The results show that the cohesion is 0.078 MPa and the internal frictional angle is 15.76°, which are lower considerably than that of the rock mass with cohesion of 16.55 MPa and the internal frictional angle is 48.2°. The steps of the back analysis method are as follows. Firstly, it is assumed that structural planes of J1-J4 are consistent with Mohr-Coulomb strength criterion; and the rock mass is homogeneous elastic and isotropic. Secondly, the equilibrium equations with the cohesion and internal frictional angle for the unknown parameters are given based on that the structural planes are under the state Of the limit equilibrium. Thirdly, carry on the 3D numerical calculation using the software of FLAC3D, extract the data needed for solving the above equations from the calculation results, substituting the above extracting data into the corresponding equation, and then four linear equations of two unknowns will be attained. Fourthly, the values of the long-term shear strength parameters, cohesion and internal frictional angle, of the structural planes can be obtained by solving this contradictory equations.