动载频率对砂岩冲击岩爆影响的实验研究

Experimental study of the effect of loading frequency on the impact rockburst of sandstone

冲击岩爆是指岩体开挖卸荷后,巷道结构已经形成且处于较为稳定的状态,在受到周围的工程扰动冲击后,在动静组合荷载作用下导致岩石剧烈弹射破坏的现象。利用冲击岩爆实验系统,开展不同动载频率条件下的冲击岩爆实验研究。通过图像采集系统拍摄试样洞室内部的岩爆全过程图像,获取冲击岩爆不同阶段的破坏特征现象,岩爆孕育破坏过程可划分为平静阶段、颗粒弹射阶段、局部鼓起阶段、碎屑剥落阶段、贯通破坏阶段和岩爆阶段。岩爆的爆坑截面呈V型,随动载频率增大,V型爆坑的破坏更加集中,爆坑呈现“闭合”趋势,即爆坑呈现“窄而深”的特征。动载频率对冲击岩爆破坏的剧烈程度有明显影响:随着动载频率增大,岩爆破坏阶段声发射的活动性增强,释放能量更多,岩爆碎屑破碎程度更高,能量耗散增多,岩爆剧烈程度增强。

After the excavation unloading of rock mass,the formed roadway structures are in a relatively stable state. Disturbed by engineering disturbance,strain energy is accumulated in the rock mass surrounding the roadway.The surrounding rock mass may fail catastrophically under such combined dynamic and static loads,which is defined as impact rockburst. In this paper,the rockburst experiment was carried out under different dynamic load frequencies. Using the image acquisition system,pictures of the whole process of destructive rockburst inside the sample cavern were captured to reveal the destructive characteristics of impact rockburst. Resutls show that the incubation and destruction process of the rockburst can be divided into the calm stage,the particle ejection stage,the local drum stage,the detrital exfoliation stage,the penetration failure stage and the rockburst stage. The crosssection of the blast crater of a rock burst is V-shaped. As the frequency of the dynamic load increases,the damage of the V-shaped blast crater becomes more concentrated,and the blast crater becomes narrower and deeper. The dynamic load frequency thus has a significant impact on the intensity of impact rockburst failure. With increasing the dynamic loading frequency,the acoustic emission increases in the rockburst stage,releasing more strain energy.In addition,the fragmentation degree and the intensity of rockburst also increase with the loading frequency.