冲击载荷作用下砂岩的动力学特性及损伤规律

Experimental test and damage characteristics of sandstone under uniaxial impact compressive loads

在单次冲击和重复冲击载荷作用下,利用大直径霍普金森压杆(SHPB)试验装置,对砂岩的动力学特性进行试验研究。从岩石的细观裂纹扩展和能量吸收的角度,分析岩石的破坏过程。基于Weibull分布的统计损伤理论,计算试件的损伤度,并结合应力-应变曲线分析岩石损伤度的演化规律。研究结果表明:砂岩的动态抗压强度和单位体积吸收能均表现较强的应变率效应,分别与应变率呈指数函数关系和线性关系。在重复冲击试验中,随着重复冲击作用次数的增加,试件的弹性模量降低,屈服应变增加,屈服应力呈降低趋势。此外,损伤度随着应变的增加逐渐增大,在应力-应变曲线的峰值强度处,损伤度出现一个明显的拐点,即在微裂纹进入不稳定扩展阶段,岩石损伤度迅速增大。

The experiments on dynamic mechanical performance of sandstone were carried out under single impact and repeated impact loadings by using a large diameter split Hopkinson pressure bar （SHPB）. The failure process of sandstone specimen was analyzed from the perspective of the microscopic crack growth and energy absorbency. The damage degree of specimens was calculated by using a statistical damage theory based on Weibull random distribution and its evolution law was analyzed with the stress-strain curves. The results show that, the dynamic compressive strength and the absorbing energy per unit volume of sandstone are strain rate dependent. The relationship between dynamic strength and average strain rate is approximately exponential function, and for the absorbing energy per unit volume, the strain rate effect can be expressed by linear approximation. In repeated impact tests, with the increase of repeated action times of impact loads, the elastic modulus of sandstone decreases, the yield strain increases and the yield stress of specimens shows a decreasing trend. In addition, in the process of impact loading, the sandstone damage degree increases with the increasing of strain. At the peak of the stress-strain curve, the damage degree has an inflection point, which means that rock damage rapidly increases when the microcracks propagation runs into the unstable phase.