冲击荷载对具有轴向静应力红砂岩应力波传播速度的影响特性

岩体工程爆破开挖时，距爆源不同距离处的围岩体承受不同大小的冲击荷载和地应力。为研究冲击荷载和地应力对岩石应力波传播速度的影响，利用改进SHPB试验装置对红砂岩进行应力波传播试验，设置7个等级的轴向静应力和冲击速度，分别模拟工程中的地应力和冲击荷载大小。基于试验得到入射波和透射波起跳点的时间差，计算岩石的应力波传播速度，得到静应力和冲击速度对应力波传播速度的影响规律。构建岩石应力波传播速度与冲击速度的关系经验模型，探索拟合参数随轴向静应力的变化规律。通过测量冲击试验后岩石的声波波速，得到受载后岩石声波波速随冲击速度的变化规律，探究动载荷对岩石应力波传播速度的影响机理。研究结果表明，具有轴向静应力岩石的应力波传播速度随冲击速度的增加先增大后减小，二者呈高斯函数的变化关系。轴向静应力显著影响应力波传播速度与冲击速度的变化关系，各个拟合参数随着轴向静应力的增大呈现不同的变化趋势。在不同的轴向静应力工况下，受载后岩石的声波波速随着冲击速度的增大呈现“平缓减小—急剧减小”的变化趋势。研究结果有助于分析深部工程岩体爆破开挖应力波的传播规律以及邻近结构的稳定性分析。

Effect of dynamic loading on the propagation velocity of stress waves in red sandstone under axial static stress

Due to the excavation unloading effect and the amplitude attenuation of stress wave, the rock masses locating the different distances away from the blasting source are subjected to different geostress and impact loadings during the blasting excavation of underground rock mass. To study the influence of different impact loading and geostress on the propagation velocity of rock stress wave, a modified Split Hopkinson Pressure Bar (SHPB) system is used to carry out the stress wave propagation test on red sandstone, axial static stress and impact velocity of 7 sizes were set respectively to simulate the size of in-situ stress and impact load in engineering. Based on the time difference between the starting points of the incident and the transmitted waves, the propagation velocity of the stress wave at the starting point of the rock is calculated. The effects of static stress and impact velocity on the propagation velocity of stress wave are analyzed. The empirical model of stress wave propagation velocity and impact velocity is established. The variation of fitting parameters with axial static stress was explored. By measuring the acoustic wave velocity of rock after impact test, the variation law of acoustic wave velocity of rock under load with impact velocity is obtained, and the influence mechanism of impact load on the propagation velocity of rock stress wave is explored. The results show that the stress wave propagation velocity of rock with axial static stress increases first and then decreases with the increase of impact velocity, and the two are gaussian function. Axial static stress significantly affects the relationship between stress wave propagation velocity and impact velocity, and each fitting parameter shows different variation trend with the increase of axial static stress. Under different axial static stress conditions, the acoustic wave velocity of rock under load presents a trend of "gently decreasing to sharply decreasing" with the increase of impact velocity. The results are helpful to the analysis of stress wave propagation in blasting excavation of deep engineering rock mass and the stability analysis of adjacent structures.