基于颗粒离散元模型的不同加载速率下花岗岩数值试验研究

不同加载速率条件下岩石的力学特性，对于其动载下破裂内在机制的研究具有积极的意义。基于颗粒流理论，通过黏结颗粒模型（bonded particle model，简称BPM）虚拟实现不同加载速率0.001～0.500 m/s下花岗岩单轴压缩和巴西劈裂试验，定量分析加载速率对应力-应变、破裂形态、应变能率及声发射的影响。结果表明：单轴抗压强度和抗拉强度及其对应峰值应变随加载速率增加而非线性增长；单轴压缩作用下，随加载速率增加，试样由单一斜截面破坏向多斜截面破坏转变，且主控裂隙带宽度急剧增大，由裂纹数量及水平向高应变率区域变化规律可明显看出，试样破坏程度随着加载速率增加而逐渐加剧；巴西劈裂作用下试样从一条主控裂隙向多条主控裂隙转变，且裂纹向圆盘试样两侧边缘部分延伸，破坏程度加剧；单轴压缩和巴西劈裂作用下，声发射事件及应变能率均随加载速率增加而呈现出非线性增长趋势。

Numerical experiments on rate-dependent behaviors of granite based on particle discrete element model

Mechanical properties of rocks at different loading rates have positive effects on their inner failure mechanisms under dynamic loading conditions. Numerical simulations of uniaxial compression and Brazilian tests are conducted on granite specimens using the bonded particle model (BPM) in particle flow code (PFC2D). To quantify rate-dependent behavior of compression strength, tensile strength, failure modes, strain energy rate and acoustic emission, four different loading rates are chosen from 0.001 to 0.500 m/s. The uniaxial compression strength (UCS) and its corresponding strain, and the tensile strength and its corresponding strain increase nonlinearly with loading rate. The failure pattern and damage degree are also influenced by the loading rate. It is found that specimens under compressive loading have a single inclined section at a lower loading rate, while have several oblige section forms at a higher loading rate. In addition, crack numbers and high horizontal strain rate distributions show that the failure zone area and damage degree increase with increasing loading rate. In Brazilian tests, the failure modes change from one primary crack to several major cracks as loading rate increases. Cracks extend to the edge of circle specimens, and loading rate exacerbates damage degree. Additionally, acoustic emission counts and strain energy rates of specimens in both tests increase in nonlinear forms with increasing loading rate.