循环载荷作用下岩石声发射时空演化规律

利用先进的声发射测试分析系统对细粒砂岩进行了声发射定位试验。通过对循环载荷作用下细粒砂岩声发射定位试验研究,分析循环载荷作用下岩石变形破坏全过程的声发射时空演化特征及其损伤演化规律。试验结果表明:静态加载阶段的声发射信息很好地反映了岩石在压密阶段、弹塑性变形阶段的损伤演化规律;循环阶段初期声发射都由小裂纹产生的小事件组成,持续时间及能量值都比较小,空间定位结果显示了事件大都在静态加载阶段形成的成核区产生,且空间事件点变化不快;循环中期声发射能量在时间上变化不大,偶有起伏,空间上事件点变化缓慢,每循环只有少量增加,在时空上都处于一个稳定发展阶段;循环末期每循环的声发射事件数、能量值都急剧增加,特别是破坏阶段达到最大值,事件点由能量高、持续时间长的大事件组成,空间演化迅速,事件点在成核区不断聚集并快速连接,不断向顶部扩散,最后容汇贯通形成宏观破裂面;峰后由于破裂面相互滑动摩擦带动附近的弱结构单元形成新损伤,继续产生声发射,且在完全停止加载后因岩石内部寻求新应力场平衡仍有少量声发射。

Space-time evolution rules study of acoustic emission locations in rock under cyclic loading

An acoustic emission(AE) location experiment was performed on sandstone using an advanced AE test system.The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE.The results show that: AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase;At the beginning of cyclic loading with low duration time and energy,AE events came from a small crack.The location result showed that most events occurred in the core zone forming at the static loading process and the location points changed slowly.AE energy changed little during the metaphase of the cyclic process.There was a modest increase of location points in every cycle.The tendency of steady development could be predicted from the AE location events.At the end of each cyclic loading,the quantity of AE events and energy increased rapidly,reaching a maximum at the last cycle.AE events had high energy and duration time.Location events changed quite rapidly,and assembled and linked continuously in the core zone.At the same time,they expanded to the top of specimen.A macroscopic crack finally formed.In the post-failure process,some AE events still existed due to fracturing of gliding friction.Owing to the inner stress balance of rock even after loading stopped,minor AE events still occurred.