煤样三轴循环加卸载力学特征颗粒流模拟

基于煤样常规三轴试验，使用颗粒流程序PFC得到了一组能够较真实反映煤样宏观力学行为的细观参数。在此基础上，对煤样进行不同围压下循环加卸载颗粒流模拟试验，分析了不同围压下煤样的宏观参数、裂纹扩展过程及其之间的关系。通过分析弹性模量和塑性应变随加载轴向应变的变化规律，表明弹性模量随加载轴向应变先增大后减小、塑性应变随加载轴向应变先稳定增加后快速变化，证明了使用颗粒流程序模拟循环加卸载是可行的。其后对循环加卸载过程进行分析，结果表明裂纹数目的非“记忆”行为随加载的进行逐渐加强，峰后微裂纹主要产生于宏观裂纹之间的相互摩擦。结合裂纹在试样内的破裂过程分析，表明剪切带的形成是造成弹性模量和塑性应变出现拐点的主要原因，对试样在循环荷载作用下的破裂过程有了一定的认识。

Particle flow simulation on mechanical behavior of coal specimen under triaxial cyclic loading and unloading

Based on the experimental results of coal samples under conventional triaxial compression,a set of microscopic parameters in particle flow code (PFC) reflecting the macroscopic mechanical behavior of coal samples were obtained.And the cycle loading-unloading experiments of the coal samples under different confining pressures in PFC were carried out to analyze the macroscopic parameters and microcrack propagation of sandstone to find the connections.Through the analysis of the change law of elastic modulus and irrecoverable strain with axial strain,it is found that the elastic modulus increases first before a decrease and the irrecoverable strain grows steadily then changes rapidly with axial strain,which prove it is workable to simulate the circulated load-reload process with PFC.Then the whole process was analyzed,which indicates the non-memorial behavior of the crack is reinforced and the micro-crack after peak is mainly occurred due to the mutual friction between the macro-cracks.Considering the crack development within the templates,the occurrence of shear section is the main cause resulting in the change of elastic modulus and irrecoverable strain,and thus the whole propagation of the sample under cyclic loading-reloading is better understood.