基于三维裂隙网络的岩体剪切特性尺寸效应分析

为研究复杂裂隙岩体剪切特性的尺寸效应，以西藏怒江松塔水电站PDC3平硐为例，在现场采集裂隙信息的基础上，基于颗粒流PFC^3D软件通过统计学方法及蒙特卡洛原理生成三维裂隙网络，构建等效岩体，进行大尺度直剪模拟试验得到裂隙岩体的抗剪强度、内摩擦系数及内聚力，分别研究其尺寸效应并确定不同参数下的REV尺寸，继而对相关参数和试样尺寸分别进行非线性回归拟合，探究其函数关系。结果表明：抗剪强度、内聚力及内摩擦系数随着试样尺寸的变化而趋于稳定，且不同参数得到的REV大小不同；综合分析不同参数的REV尺寸，得出研究区裂隙岩体的剪切特性REV尺寸为11 m×11 m×11 m;通过函数关系拟合，抗剪强度、内聚力和内摩擦系数与试样尺寸之间均存在指数函数关系。该成果为研究复杂裂隙岩体的力学REV以及合理确定力学参数提供了依据。

Analysis of size effect for shear characteristics of rock mass based on 3D fracture network

In order to study the size effect of the shear characteristics of complex fractured rock mass, taking PDC3 adit of Songta Hydropower Station in Nujiang, Tibet as an example, on the basis of on-site fracture information collection, based on PFC^3D software, a 3D fracture network was generated by statistical method and Monte Carlo principle, and the equivalent rock mass was constructed. The shear strength, internal friction coefficient and cohesion of fractured rock mass were obtained by large-scale direct shear test, and the size effect of the fractured rock mass was studied and the REV size under different parameters was determined. Then, the related parameters and sample sizes were fitted by nonlinear regression to explore their functional relationship. The results show that the shear strength, cohesion and internal friction coefficient tend to be stable with the change of sample size, and the REV obtained from different parameters are different. Comprehensive analysis of REV size of different parameters shows that the REV size of fractured rock mass for the shear characteristics in the study area is 11 m×11 m×11 m. By fitting the function relationship, there are exponential function relationships between shear strength, cohesion and internal friction coefficient and sample size. These results provide a basis for studying the mechanical REV of complex fractured rock mass and reasonably determining the mechanical parameters.