基于颗粒流数值仿真的不同围压下花岗岩加载速率效应研究

The Effect of Loading Rate of Granite Under Confining Pressure Based on Particle Flow Simulation

基于拉西瓦水电站花岗岩常规三轴试验结果,利用PFC得到该花岗岩宏观力学特性的细观参数,在此基础上进行不同围压及加载速率下三轴压缩数值试验,研究花岗岩的加载速率效应。结果表明,相同围压下,加载速率较低时,应力应变曲线反映出花岗岩呈脆性破坏,随着加载速率增加,花岗岩由脆性破坏向延性破坏转化;同一围压下,随着加载速率的升高,花岗岩峰值强度、损伤应力、粘聚力及内摩擦角均呈增大趋势;随围压升高,归一化损伤应力整体增加,加载速率对峰值的提高作用降低,速率由0.005 m/s增加至0.300 m/s时,峰值强度增幅由7.2%降为5.0%。粘聚力、内摩擦角与加载速率均呈线性关系,相关系数分别为0.95、0.97。研究成果可为工程实践提供参考。

A set of microscopic parameters in PFCreflecting the macroscopic mechanical characteristics of granite were obtained based on the laboratory experimental result of granite under conventional triaxial compression. The granite triaxial compression test was carried out under different confining pressures and loading rates, and the loading rate effect of granite was studied. The results are as follows. Stress-strain curves exhibit brittle characteristics at low loading rates, and the failure style changes from brittle to ductile as the loading rate increasing. Peak granite strength, damage stress, cohesion and internal friction angle all tend to increase with increasing loading rate at the same confining pressure. With the increase of confining pressure, the normalized damage stress increases, and the effects of loading rate on the increase of peak value decay. When the velocity increases from 0.005 m/s to 0.300 m/s, the increase of peak strength decreases from 7.2 % to 5.0%. There was a linear relationship between cohesion and internal friction angle and loading rate, and the correlation coefficients were 0.95 and 0.97, respectively. Research results can be valuable reference to engineering practice.