断续节理直剪试验与PFC2D数值模拟分析

 在以往有关断续节理模型试验和数值模拟的研究基础上，设计不同连通情况和法向应力的断续节理模型材料直剪试验，并采用颗粒流离散元软件PFC2D对模型试验进行全真数值模拟。以贯通节理试样、完整试样的剪应力–应变数值模拟曲线和模型试验曲线吻合作为PFC细观力学参数选取准则，并利用获得的细观力学参数对共面断续节理试样直剪试验进行数值重现。对比分析数值模拟曲线和模型试验曲线，对断续节理受剪贯通的力学机制进行研究。根据模型试验和数值试验的成果，分析断续节理预剪面上应力随剪应变的演化过程，发现剪切过程中的剪胀效应使得岩桥承担更多的压应力，从而提高了岩桥的抗剪强度。对断续节理岩体在直剪加载条件下的破坏机制进行讨论，将整个剪切过程分为线弹性阶段、初裂阶段、峰值阶段、峰后阶段及残余阶段5个阶段。

DIRECT SHEAR TESTS AND PFC2D NUMERICAL SIMULATION OF INTERMITTENT JOINTS

The research results of model tests and numerical simulation in two different loading conditions，triaxial and direct shear，are summarized. By conducting model tests on integrated samples and intermittent joints samples，shear strengths under different normal stresses are obtained. Also，the changing trends of shear strength under various connectivity rates are analyzed. The entire process of direct shear test is numerically simulated using particle flow code in 2 dimensions(PFC2D). In order to make the stress-strain curve of numerical simulation accord with experimental one about both integrated samples and through samples，the mechanical parameters between particles are adjusted. Through adopting the same particle geometric parameter，the numerical models of intermittent joints under different connective conditions are rebuilt. At the same time，the rock bridges and joints in testing samples with the fixed particle contacting parameters are endowed，and a series of direct shear tests are conducted. Then the failure process and mechanical parameters in both micro-prospective and macro-prospective are obtained. By synthesizing the numerical and testing results and analyzing the evolutionary process of stress and strain on intermittent joints plane，it is concluded that the shear strength of rock bridges is increased due to the centralization of compressive stress on it. At last，the failure mechanism of intermittent joints rock under direct shear condition is discussed，meanwhile，the whole shear process is divided into five phases，i.e. linear elastic phase，fracture initiation phase，peak value phase，after-peak phase and residual phase.