梯度应力作用下不同中主应力对岩爆影响的模型试验研究

Model experimental investigation on influence of different intermediate principal stresses on rockburst under gradient stress

为探究围岩切向应力梯度加载过程中不同中主应力对岩爆孕育及破坏的影响,借助自主研发的气液复合加载装置,开展类岩石材料模型试件在3种不同中主应力条件下的真三轴岩爆模拟试验。试验过程利用高速摄像机与声发射监测系统进行监测,对比分析各试件岩爆宏观破坏差异与声发射参数演化规律。研究结果表明:随中主应力增大,试件破坏荷载增大,岩爆破坏瞬时突发性增强,岩爆碎屑总质量及各粒径碎屑质量增加,试件破坏规模越大。加载前、中期高中主应力条件下试件的声发射活动减弱,表明高中主应力条件抑制了试件损伤与裂隙发育;加载后期高中主应力条件下试件的声发射振铃计数与能量释放愈发集中且能量峰值与累计值提高,声发射b值骤降至更低水平,高主频幅值点占比增加,表明高中主应力条件加剧了试件损伤与裂隙发育,大尺度裂纹及剪切裂纹数目增多,岩爆瞬间能量释放更猛烈,致使试件破坏更严重,岩爆剧烈程度更高。

To investigate the effect of various intermediate principal stresses on rockburst incubation and failure during tangential stress gradient loading,a series of true triaxial rockburst model experiments on quasi-rock material specimens under three intermediate principal stress conditions was conducted using a self-developed gas-liquid combined loading apparatus.A high-speed camera and an acoustic emission monitoring system recorded the test data.This paper compared and analyzed the macroscopic failure differences of the specimens and the evolution characteristics of acoustic emission parameters.The results indicate that the failure load,instantaneous burst intensity of rockburst,total mass of rockburst debris,mass of debris of each particle size,and scale of specimen failure increase with higher intermediate principal stress.During loading,specimens under high intermediate principal stress show weakened acoustic emission activity in the early and middle stages,revealing that the high intermediate principal stress suppresses the damage and crack development.In the later stages,the acoustic emission ringing count and energy release of the specimens under high intermediate principal stress become more concentrated,and the energy peak and cumulative values increase.The acoustic emission b-value drops sharply to a lower level,and the proportion of high main frequency amplitude points increases,indicating that high intermediate principal stress exacerbates the damage and crack development.The number of large-scale and shear cracks increases,leading to more violent instantaneous energy release,more severe failure,and higher intensity of rockburst.