节理厚度对应力波传播和动力特性影响的SHPB试验

SHPB tests of the influence of different joint thickness on numerical simulation of stress wave propagation and dynamic behavior of red sandstone

为了研究含平行节理岩体对地下工程活动的影响,采用不同节理厚度的红砂岩试样,借助分离式Hopkinson压杆(SHPB)装置,对节理红砂岩试样的应力波传播和破坏模式进行研究,结合有限元软件ANSYS/LS-DYNA对试验过程进行了数值模拟,并且增加了节理厚度为2 mm和6 mm的模拟内容。研究结果表明:红砂岩中平行节理的存在影响着应力波的传播。随着节理厚度的增加,反射系数呈线性增大,透射系数呈弱幂函数减小,其最小值为52.28%,红砂岩的破坏形态变化不明显,但靠近入射杆一端的破坏程度变大,动态峰值强度呈先下降后上升的趋势,相较于初始值其峰值强度降低了6.56%~33.77%,透射系数和峰值强度曲线的变化趋势相似;节理岩石的入射能、反射能和透射能均随冲击速度的增大呈增加趋势,但入射能比反射与透射能敏感性更大,损伤变量随冲击速度呈二次函数增长,其值越大,岩石的损伤破碎程度越高。

To study the influence of rock mass with parallel joints on underground engineering activities,red sandstone specimens with different joint thickness are used to study their stress wave propagation and failure mode by split Hopkinson pressure bar(SHPB)apparatus,the simulation content with joint thicknesses of 2 mm and 6 mm is added by the finite element software ANSYS/LS-DYNA.The results indicate that the existence of parallel joints in red sandstone affects the propagation of stress waves.With the increase of joint thickness,the reflection coefficient increases linearly and the transmission coefficient decreases by a weak power function with the minimum value of 52.28%.The failure mode of red sandstone is not obvious,but the failure degree near the incident rod becomes larger.The dynamic peak stress first decreases and then increases.Compared with the initial value,the peak stress decreases by 6.56%~33.77%,and the variation trend of transmission coefficient and peak stress curve is similar.The incident energy,reflection energy and transmission energy of jointed rock increase with the increase of impact velocity,but the incident energy is more sensitive than the reflection and transmission energy.The damage parameter increases with the impact velocity as a quadratic function.The larger the value is,the higher the damage degree of rock is.