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由于开挖卸荷效应以及原岩应力的复杂性,围岩体承受的静应力大小具有动态变化特点。为了研究静应力大小对岩石应力波传播的影响,利用动静组合加载试验装置,对红砂岩长试件进行小扰动的应力波传播试验,试件轴向静应力分别设置为13个等级。通过应力波传播速度和幅值随传播距离、传播时间以及静应力的衰减规律,研究不同静应力条件下应力波的传播衰减特性。结果表明,相同轴压下,不同测点处应力波形状基本相同;不同轴压下,相同测点处应力形状变化较大,轴压越大,应力波尾部出现的拉伸波越大。随着轴向静应力的增加,岩石纵波波速呈“快速增加–平缓发展–急剧减小”的趋势,轴向静应力与单轴抗压强度之比?s/?c=30%和?s/?c=55%是其2个应力分界点。相同轴压下,应力波幅值随传播距离及传播时间都具有良好的指数关系;随着轴压的增加,空间和时间响应强度逐渐减小,幅值空间衰减系数和时间衰减系数呈“快速减小–平稳发展–急剧增大”的趋势。随轴压增加,相同测点处幅值随轴压衰减系数??s先减小后增大,离冲击端越近测点处的??s变化越敏感。
Due to the unloading effect of excavation and the complexity of the original rock stress, the dynamic stress characteristics of the surrounding rock mass have the characteristics of dynamic changes. In order to study the effect of static stress on the propagation of stress wave in rock, a small disturbed stress wave propagation experiment was carried out on the long sandstone samples using dynamic and static loading device. The axial static stress of specimens was set to 13 levels respectively. The propagation and attenuation characteristics of stress waves under different static stresses are studied by the propagation laws of the propagation velocity and amplitude of the stress wave with propagation distance, propagation time and static stress. The results show that the shape of stress wave is basically the same at different measuring points under the same axial pressure. The stress shape changes greatly at the same measuring point under different axial compressions. The larger the axial compression, the larger the tensile wave appears at the tail of the stress wave. With the increase of axial static stress, the longitudinal wave velocity of rock shows a tendency of “rapid increase-gentle evolution-sharp decrease”, and the ratio of axial static stress to uniaxial compressive strength is 30% and ? s /? c = 55% is its two stress demarcation points. Under the same axial compression, the amplitude of stress wave has a good exponential relationship with the propagation distance and propagation time. With the increase of axial compression, the spatial and temporal response strength decreases gradually, and the amplitude attenuation coefficient and time attenuation coefficient show “ Rapid reduction - steady development - sharp increase ”trend. As the axial pressure increases, the amplitude at the same measuring point decreases first and then increases with the axial pressure attenuation coefficient ?? s, and is more sensitive to the change of ?? s near the measuring point at the impact end.