不同冲击强度下的砂岩动态力学特性试验研究

为研究冲击强度对岩石动态力学特性的影响,以改装的霍普金森压杆(SHPB)装置对砂岩进行了不同冲击强度下的动力学试验,测得了动态应力-应变曲线和应力波波形。然后,基于试验数据分析了冲击强度对砂岩强度、应变特性以及能量耗散规律的影响。结果表明:动态应力-应变曲线未出现压密阶段直接进入弹性阶段,冲击强度越大,应力-应变路径越长;岩样以破碎形态为主,破碎程度与冲击强度呈正相关;随着冲击强度增大,平均抗压强度和平均应变呈线性增长,而平均应变率呈指数增长;平均抗压强度和平均弹性模量随平均应变率呈线性增加。冲击强度越大,入射能和反射能值显著提高而透射能变化不明显,透射系数和反射系数分别呈幂函数增长和对数降低。砂岩吸收能随冲击强度和平均抗压强度分别呈指数关系和对数关系。由此表明,不同冲击强度对砂岩应变特征、强度特征以及能量耗散具有显著影响,适当增加冲击强度可有效提高砂岩吸收能,进而提高破岩效果。

Experimental study on dynamic mechanical properties of sandstone under different impact strength

To reveal the influence of impact strength on dynamic mechanical properties of rock, dynamic failure tests of sandstone under different impact strength were carried out with the modified Hopkinson Pressure Bar (SHPB) device, and dynamic stress-strain curve and stress waveform were measured. Then, influence of impact strength on sandstone strength, strain characteristics and energy dissipation is analyzed based on experimental data. The results show that the dynamic stress-strain curve directly enters the elastic deformation stage without a compression stage, and the greater the impact strength, the longer the stress-strain path. The impacted rock samples include fracture and fragmentation, and the degree of fragmentation is positively correlated with the impact strength. Besides, average dynamic compressive strength and average failure strain both increase linearly with increasing impact strength while the average strain rate and impact strength increase in accordance with an exponential function. The larger the impact intensity is, the higher the incident energy and reflection energy are while the transmission energy does not change obviously. The transmission coefficient and reflection coefficient respectively increase in power function and decrease in logarithm, and the absorption energy respectively increase exponential and logarithmic with impact strength and average compressive strength. The conclusions show that different impact strength has a significant influence on strain characteristics, strength characteristics and energy dissipation of sandstone.