In order to investigate the tensile characteristics and energy dissipation laws of green sandstone under different loading rates, the macro-micro mechanical response relationship of green sandstone was established by combining indoor experiments and micro parameter calibration. The mechanical properties, fracture characteristics, crack propagation, and energy dissipation laws of green sandstone under different loading rates were studied using the particle flow code. The results are as follows. 1) With the loading rate of 0.1 m/s as the boundary point, the maximum radial stress-strain of green sandstone exhibits a sequentially slow and rapid increasing trend, and the microelements formed after fracture accelerate to fracture again in accordance with the Brazilian splitting method. 2) When the loading rate is less than 0.1 m/s, the tensile cracks in the green sandstone show the trend of slight fluctuations, and no shear cracks appear. When the loading rate is more than 0.1 m/s, tensile cracks increase rapidly and shear cracks begin to appear, but the number is relatively small. The propagation direction of crack is perpendicular or at a certain angle to the loading direction, and relatively less in the horizontal direction. There is a negative correlation between crack propagation time and loading rate. When the loading rate is 0.1~1 m/s, the propagation time of crack tends to be stable, with a range of 1.757–0.951 μs. 3) When the loading rate is less than 0.1 m/s, except for significant fluctuations in kinetic energy, the dissipated energy basically shows a trend of small fluctuations. However, when the loading rate is more than 0.1 m/s, the dissipated energy increases rapidly. The energy loss (kinetic energy) accounts for the main part, while the energy used for crack propagation (damping energy and friction energy) is more than the energy used for crack generation (bond failure energy). This study not only reveals the characteristics of rock fracture and energy dissipation at the microscopic level, but also provides reference for the rational selection of loading methods in rock-crushing processes. 

green sandstone, loading rate, Brazilian splitting, tensile properties, particle flow code, crack propagation, energy consumption, utilization efficiency of energy

为探究不同加载速率下青砂岩抗拉特征及能量耗散规律, 结合室内试验与细观参数标定, 建立青砂岩宏观–细观力学响应关系, 采用颗粒流程序研究青砂岩在不同加载速率下的力学特性、破裂特征、裂纹扩展与能量耗散规律, 得到如下结果。1) 以加载速率0.1 m/s为分界点, 青砂岩径向最大应力–应变呈现先缓慢、后快速增加的趋势, 破裂后形成的微元体按照巴西劈裂方式再次加速破裂。2) 加载速率小于0.1 m/s时, 青砂岩拉伸裂纹呈现小幅度波动趋势, 未出现剪切裂纹; 加载速率大于0.1 m/s时, 拉伸裂纹快速增加, 剪切裂纹开始出现, 但数量较少。裂纹扩展方向与加载方向垂直或呈一定的角度, 水平方向上相对较少。裂纹扩展时间与加载速率负相关, 加载速率为0.1~1 m/s时, 裂纹扩展时间基本上趋于稳定(1.757~0.951 μs)。3) 加载速率小于0.1 m/s时, 除动能波动较大外, 其余耗散能量基本上呈现小幅度波动的趋势, 加载速率大于0.1 m/s时, 耗散能量均快速增加。能量损失(动能)占主要部分, 用于裂纹扩展的能量(阻尼能与摩擦能)大于裂纹生成的能量(黏结破坏能)。研究结果在细观层面深入地揭示了岩石破裂特征及能量耗散规律, 亦可为岩石破碎时加载方式的合理选择提供参考。