动荷载与地应力对岩石响应特性的影响试验研究

Effect of dynamic loads and geo-stresses on response characteristics of rocks

地下岩体工程爆破开挖施工过程中,距爆源不同距离处地应力和动荷载大小不同,导致岩石具有不同的响应特性。为研究不同大小动荷载与地应力对岩石动态强度和变形特性的影响,利用改进的SHPB试验装置,设置5个冲击速度和轴向静应力等级,分别模拟不同大小的动荷载和地应力,对红砂岩进行三维动态压缩试验。分别分析不同冲击速度和静应力工况下红砂岩平均应变率、动态峰值应力(或动态压缩强度)、极限应变、动态变形模量的变化规律,分别构建红砂岩动态响应参数的演化经验模型,表征岩石动态响应特性。研究结果表明:(1)红砂岩应变率受冲击速度和静应力的影响较大,平均应变率随轴向静应力的增加先减小后增大,随冲击速度的增加呈幂函数增长。(2)相同三维静应力下,随着冲击速度的增加,红砂岩峰值应力和极限应变都呈幂函数增加。(3)相同冲击速度下,随着轴向静应力的增加,红砂岩峰值应力先增大后减小,极限应变先减小后增大。(4)随着轴向静应力的增加,红砂岩临界冲击速度与动态压缩强度均先增大后减小。研究结果有益于岩石动力学理论的完善,也有助于根据工程爆破炸药类型和用量预测围岩体的响应特性及稳定性。

In the blasting process of underground rock mass,the geo-stresses and dynamic loads are different at different distances from the blasting source,which leads to different response characteristics of rocks. In order to study the influence of dynamic loads on the dynamic strength and deformation characteristics of rocks with different geo-stresses,a modified SHPB test device was used to carry out three-dimensional dynamic compression test on red sandstone by setting five impact velocities and five axial static stress levels respectively to simulate different dynamic loads and geo-stresses. The variation rules of average strain rate,dynamic peak stress(or dynamic compressive strength),ultimate strain and dynamic deformation modulus of red sandstone under different impact velocities and static stress conditions were analyzed respectively,and the evolution empirical models of dynamic response parameters of red sandstone were built to characterize the dynamic response characteristics of rocks. The results show that:(1) the strain rate of red sandstone is affected by the impact velocity and the static stress,and the average strain rate decreases first and then increases with increasing the axial static stress and increases as a power function with the impact velocity,(2) under the same three-dimensional static load,the peak stress and ultimate strain of red sandstone increase by a power function with the impact velocity,(3) under the same impact velocity,with increasing the axial static stress,the peak stress of red sandstone increases as a power function and the ultimate strain also gradually increases,and(4) with increasing the axial static stress,the critical impact velocity and dynamic compression strength of red sandstone both increase first and then decrease. The research results are beneficial to the perfection of rock dynamics theory and the prediction of the response characteristics and stability of surrounding rock mass according to the type and amount of explosives in engineering blasting.