中等应变速率对砂岩破坏形态和力学性质的影响

以砂岩为研究对象,根据砂岩的颗粒分析试验、抗压强度、抗拉强度和强度试验结果,在颗粒流程序下,通过fish语言编程,虚拟实现了砂岩数值试件和单轴压缩试验,设计10-3、5×10-3、10-2、2×10-2、5×10-2、10-1、2×10-1s-1这7个应变率下的单轴压缩试验.分析应变率对砂岩破裂形态、裂纹数量和扩展、应力-应变曲线和能量转换的影响.结果发现:应变率的增加破坏了优势剪切带的发展,使得剪切带等速发展,材料由剪切破坏向锥形破坏发展;材料的力学性能表现出极大的伪增强,应力-应变曲线上扬、斜率提高、峰值提高,峰后曲线震荡剧烈;裂缝数量增多,其中拉裂缝减少,剪切裂缝增多;边界输入能量增加,造成加载过程中材料的摩擦能、动能和应变能单调增大,摩擦能增大说明剪切裂缝增多,动能增大说明破坏剧烈,应变能增大说明更容易产生岩爆现象.

Rupture and mechanics behavior of sandstone affected by medium strain rate

Taking sandstone as object, a virtual specimen and uniaxial compression test of sandstone was conducted under particle flow code with its embedded fish language according to the experimental results of sandstone’s grain analysis, compression strength, tensile strength and its cohesion or friction angle tests. The uniaixal compression tests with seven kinds of strain rate such as 10-3，5×10-3，10-2，2×10-2，5×10-2，10-1，2×10-1 s-1 were designed to analyze the effect of strain rate. The influences of rupture process, crack number and propagation, curve of stress and strain, energy transformation derived from strain rate were analyzed. Results show that the increase of strain rate ruins the advantageous shear zone’s development, which makes the shear zone expand with the same velocity, and the material failure plane changes from shearing failure to cone breakage. The strain rate meso enhances the material mechanics and deformation features with the uplifting of stress strain curve’s slope and peak value. Total cracks increase with the decreasing tensile crack and the increasing shearing crack. The boundary energy enhances, so the friction energy, kinetic energy and strain energy monotonically increase, which illustrates the increase of shear crack, violent failure and rockburst of side.