单轴静–动相继压缩下单裂隙岩样力学响应及能量耗散机制颗粒流模拟

 针对采矿岩柱体等的静–动相继单轴压缩受力特征，采用颗粒流数值模拟试验，探讨初始单轴静态压缩的细观损伤程度对单轴动态压缩下单裂隙岩样力学性质的影响规律，并阐述其能量耗散机制。静载初始损伤程度对后续动态压缩岩样应力–应变曲线形态的影响不大，损伤岩样具有较明显的峰前损伤和峰后裂隙贯通的渐进性突跃特征。相对于全程动态压缩而言，随着初始损伤的增强，岩样强度减小明显。但后续动态压缩对岩体强度的增加起主要贡献。随初始损伤的增强，裂隙尖端法向和切向破裂应力均略有减小。随着裂隙倾角的增大，裂隙尖端法向破裂应力明显减小而切向却明显增加。初始损伤程度并不改变后续动态应变率加载岩体的最终宏观破裂模式，但初始损伤变量越大，微裂纹数量越多且局部化程度越强。能量耗散与岩体细观损伤演化具有较好的相关性。初始损伤越强，吸收相对较小的能量即可达到峰值破坏但峰后耗散能越多。随着裂隙倾角的增大，峰值强度处耗散能和储存弹性应变能更多，峰后破碎程度越高。

MECHANICAL RESPONSES AND ENERGY DISSIPATION MECHANISM OF ROCK SPECIMEN WITH A SINGLE FISSURE UNDER STATIC AND DYNAMIC UNIAXIAL COMPRESSION USING PARTICLE FLOW CODE SIMULATIONS

In view of characteristics of static and dynamic uniaxial compression，such as mining rock pillar，the influence of initial mesoscopic damage level under uniaxial static compression on mechanical properties of rock specimen with a single fissure under subsequent uniaxial dynamic compression and the energy dissipation mechanism are simulated by particle flow code. Minor influence of initial damage level under static uniaxial compression on patterns of stress-strain curves of rock specimens which are under dynamic uniaxial compression subsequently is observed. The damage at pre-peak and the crack coalescence at post-peak for damaged rock specimens behave in obvious progressions and jumps. Lower strength of specimens is presented with the increase of initial damage. But the subsequent dynamic compression suggests the strength increases drastically compared with one due to initial damage. The normal and tangential fracture stresses of crack tip are reduced slightly with the increase of initial damage. And the normal fracture stress is reduced but the tangential stress increases sharply with the increase of fissure dip angle. The final macroscopic fracture mode of specimens under subsequent dynamic compression does not change around initial damage level. However，more microcracks and stronger damage localization are observed with the increase of initial damage. The energy dissipation is closely related to the mesoscopic damage evolution of rock mass. The stronger the initial damage of rock mass is，the less energy is absorbed to reach the peak failure，but more energy is dissipated at post-peak. The more dissipation energy and stored elastic strain energy at peak strength are，the stronger damage fracture at post-peak is with the increase of fissure dip angle.