岩石节理直剪试验颗粒流宏细观分析

 基于颗粒流理论和PFC程序，在解决建模过程中悬浮颗粒的消除、恒定法向荷载伺服机制的施加、拟静力加载状态的选取等问题后，较为完善地实现岩石节理PFC数值直剪试验，并分别从宏观和细观角度深入探讨节理在直剪试验过程中的力学演化特征和破坏机制。结合已有的节理直剪试验成果，进行室内试验和计算结果的对比分析，验证计算方法的可靠性。研究成果如下：(1) 随恒定法向荷载的增大，剪切应力及其峰值时刻的剪切位移增大，节理面上黏结破坏颗粒增多，而剪切阻抗和节理剪胀效应却降低；(2) 随剪切位移的增加，节理面上粒间法向接触数不断减少，接触矢量方向逐渐向剪切荷载施加方向偏转，而粒间接触压力不断增大，裂纹不断沿节理面附近产生，破裂频数在剪切应力达到峰值时最为强烈；(3) 数值试验得到的剪切阻抗值普遍高于试验值，但减小模型颗粒半径可有效降低计算剪切阻抗值。室内试验和计算结果对比分析表明，新提出的颗粒流计算方法非常适用于岩石节理直剪试验的数值模拟，可为室内节理直剪试验和PFC节理模型细观力学参数选取的深入研究提供有益的参考。

MACRO- AND MESO-ANALYSES OF ROCK JOINT DIRECT SHEAR TEST USING PARTICLE FLOW THEORY

The numerical simulation of rock joint shear test was successfully performed using the particle flow theory based on particle flow code(PFC),by addressing the implementation issues such as floater elimination,constant normal stress servo mechanism and loading velocity specification.Based on the simulation results,the mechanical evolution law and failure mechanism during the shear test process are deeply discussed from macro-and meso-scale perspectives.The reliability of the simulations method is verified by comparing calculation results and existing data from laboratory joint shear test.The main research results are as follows:(1) With the increase of constant normal stress,the number of failure-bond particles on joint,shear stress and shear displacement at the peak shear stress increase,while the effects of shear resistance and dilatancy on joints decrease.(2) As the shear displacement increases,the number of normal contact between particles on joint decreases and contact vector direction aligns towards the direction of shear load.Furthermore,the contact force on joint continually increases with cracks developing in the joint vicinity;and the rupture frequency is found to be most intense at the peak value of shear stress.(3) The shear resistance obtained from numerical calculation is higher than that of the laboratory test.However,the calculated shear resistance can be decreased effectively by reducing the particle radius.The comparison analysis between laboratory test and calculation results shows that the particle flow calculation method proposed here is suitable for the numerical simulation of rock joint test,and it can function as a beneficial reference for deeply research on the laboratory joint shear test as well as the mesomechanical parameter determination for joint model in PFC.