高应力岩体爆破卸荷过程中应变率及应变能特征

Characteristics of strain rate and strain energy during blasting unloading of high stress rock mass

针对高应力岩体爆破开挖卸载问题,自制了一台轴向加、卸载实验测试平台,通过实验测试获得了爆破卸荷过程中岩杆的动态应变及应变率数据。实测数据表明:开挖面附近岩体的爆破加、卸载以及初始应力卸载应变率均在10^-1 s^-1量级以上,验证了高地应力区岩体爆破开挖卸荷是一动态过程。建立了初始应力卸载一维力学模型,揭示了卸载波的传播机制;通过分析爆破卸荷过程应变能密度的时空分布特征,建立了应变能密度与各阶段应变率变化规律的联系。结合实测数据,采用隐式-显式顺序求解方法,进一步分析了高应力区岩体爆破卸荷荷载各阶段应变率沿岩杆的变化规律。结果表明:爆破加载阶段的平均应变率沿杆件逐渐衰减,且衰减速度逐渐减小;爆破卸阶段平均应变率沿杆件也呈衰减趋势;而初始应力的应变能稳定释放,其平均应变率无衰减趋势。

To explore the unloading of blasting excavation in highly-stressed rock masses for hydropower stations, an axial loading and unloading test platform was independently developed. The dynamic strain and strain rate data of rock bars during the blasting process were experimentally obtained. The measured data indicate that the strain rates in the rock bars are all above 10^-1 s^-1 during the blasting loading and unloading and the initial stress unloading near the excavation face. It is verified that the unloading of blasting excavation in the highly-stressed rock mass is a dynamic process. A one-dimensional mechanical model for the initial stress unloading was established, and the propagation mechanism of the unloading wave was revealed. By analyzing the temporal and spatial distribution characteristics of the strain energy density in the blasting unloading process, the relationship between the strain energy density and the strain rate rule in various stages of blasting was established. Based on the measured data, the implicit-explicit sequential solution method was applied to further analyze the variation of strain rate along the rock bar in different stages of the loading and unloading in deep rock mass. The results show that the average strain rate and the decay rate decrease gradually in the loading stage of the blasting. And the average strain rate in the unloading stage of the blasting decreases along the bar, while the strain energy induced by the initial stress can release steadily, and the corresponding average strain rate has no attenuation trend.