高应力巷道岩爆过程及时空演化规律试验研究

Experimental study on rockburst and its spatio-temporal evolution criterion in high stress roadway

为了研究岩爆灾害的发生过程及其时空演化规律,通过含圆孔花岗岩试件进行不同侧向载荷下的岩爆模拟试验,利用微型摄像机、声发射(AE)系统和红外热像仪等监测系统,分析岩爆过程中的声发射时序、时频、时空特征及热成像温度运移规律。研究结果表明:孔洞的岩爆可分为平静期、颗粒弹射期、稳定破坏期、全面崩塌期4个阶段,岩爆试验演化过程及结果与工程现场相符,围岩曲屈破坏时σθmax≈(1.38~1.85)σc;随着侧向载荷的升高,孔洞在平静期积累的弹性应变能增加,颗粒弹射期能量释放率增大,岩爆进程加快,稳定破坏期持续时间先增加后减小,侧向载荷的增大对孔洞的承载能力起到先增强后弱化的效果;声发射振铃计数率的平静期可作为孔洞全面崩塌的前兆信号,围岩屈曲破坏前定位点开始局部集中,孔洞坍塌后定位点集中条带与试件主破裂面基本吻合,形成以圆孔为中心的“X”型共轭剪切破裂,稳定破坏期较颗粒弹射期低频比例增加,高频比例降低,低侧向载荷时破坏以中高频为主,高侧向载荷时破坏以中频为主;应力集中促使围岩红外温度场整体温度逐渐升高,呈现高温区嵌套低温条带的特点,岩爆时高温区由表面浅部向深部运移,在孔洞整体失稳坍塌前,岩爆坑温度急剧上升。

To study the mechanism of rockburst and its spatio-temporal evolution criterion,the rockburst simulation experiment was conducted using granite specimen with a perforated circular hole under different lateral load.Based on the micro camera,acoustic emission(AE)system and infrared thermal imager,the characteristics of its time-sequence,time-frequency,time-space and infrared temperature were analyzed during the test.The results demonstrated that the failure could be divided into four stages:quiet period,particle ejection period,stable failure period and collapse period.It was consistent with the engineering site.When the surrounding rock of the hole was bent and broken,σθmax≈(1.38~1.85)σc.With the growth of the lateral load,the accumulated elastic strain energy grew around the hole area during the quiet period,the energy release rate gradually promoted and the rockburst speeded up during the particle ejection period,the duration of the stable failure period first increased and then decreased.In addition,the lateral load first strengthened and then weakened the stability of the pore.The relatively quiet period of AE ringing counting rate could be regarded as the precursor signal for hole collapse.The anchor point began to focus locally before the hole failure.After the hole collapsed,the anchor point strip basically coincided with the main fracture surface of the specimen and it formed an“X”shaped conjugate shear fracture around the circular hole.In the stability failure period,the low frequency ratio was accelerated and the high frequency ratio was decreased compared with the particle ejection period.The stress concentration caused the whole infrared temperature raised gradually and presented the high temperature region nested low temperature zone.Furthermore,when rockburst occurred,the high temperature area migrated from the shallow surface to the deep area.Before the hole collapsed,the temperature of the rockburst pit rose sharply.