断续双裂隙红砂岩加载速率效应颗粒流分析

Particle Flow Simulation on Loading Rate Effects of Red Sandstone Containing Two Pre-Existing Fissures

采用颗粒流程序平行黏结模型,对不同加载速率下断续非共面双裂隙红砂岩数值试样进行单轴和三轴压缩模拟,分析了加载速率对应力-应变曲线、峰值强度、扩容特征、变形参数和破坏模式等力学行为的影响。研究结果表明:加载速率主要影响应力-应变曲线峰值强度和峰后阶段,对峰前阶段影响很小。峰值强度随着加载速率的增大呈单调增长,与围压的关系可以用Mohr-Coulomb准则表征。裂纹损伤阈值对速率的敏感性随着加载速率的增大而提高,与围压的关系可以用广义Hoek-Brown准则表征。加载速率对弹性模量和泊松比的影响很小,而弱化模量和峰值应变影响明显。高加载速率会生成更多的微裂纹,进而造成试样破坏更为严重。

Parallel-Bond Model in Particle Flow Code （PFC） was used to simulate red sandstone containing two non-coplanar fissures under uniaxial and triaxial compression at different loading rate. On basis of the simulated resuits, the influence of loading rate on the stress-strain curves, peak strength, critical damage threshold, deformation parameters and crack coalescence of pre-cracked red sandstone was analyzed. The investigation conclusions can be described as follows. The loading rate mainly impacts peak and post-peak stages of stress-strain curves. The peak strength increases as the loading rate increased. The relationship between peak strength and confining pressure can be characterized by Mohr-Coulomb criterion. Critical damage threshold for rate sensitivity increases as the loading rate increased. Relationship between critical damage threshold and confining pressure can be characterized by generalized Hoek-Brown criterion. The effect of loading rate on elastic modulus and Poisson＇ s ratio is slight, but obvious for weaken modulus and peak strain. More micro-cracks initiate under high loading rate, thus causing more serious damage to the specimen.