锁固段体积膨胀点的声发射事件能级特征

Energy Level Characteristics of Acoustic Emission Events at the Volume Dilation Point of a Locked Segment

确定锁固段体积膨胀点对识别锁固型斜坡的加速蠕变起点具有重要意义,但目前尚缺乏被普遍认可的方法。为此,采用数值模拟方法,研究了直剪应力状态下岩桥型锁固段破裂过程的声发射特征。结果表明:当锁固段被加载至体积膨胀点时,会发生显著的较高能级声发射事件,即标志性声发射事件,这可作为判识体积膨胀点的标志;标志性声发射事件能级与峰值强度点处的主震事件能级的差值基本为定值,说明两者之间可能存在内在的力学联系。以法国Mesnil-Val海岸某崩塌体为例,分析了其演化过程中的微震活动。结果表明,利用标志性声发射或微震事件判识体积膨胀点具有一定的可行性。

Determining the volume dilation point of locked segment is crucial to the identification of accelerating creep onset of locked-segment type slopes,but currently there are few methods accepted extensively.Using the numerical modeling tool,we investigate the acoustic emission(AE)characteristics during the failure processes of a rock-bridge-type locked segment subjected to direct shear.We find that characteristic AE events occur when the locked segment is loaded to reach its volume dilation point,which can be viewed as the indicator of the volume dilation point;the difference value of energy level between the characteristic AE event at the volume dilation point and the mainshock event at the peak strength point is approximately a constant,probably demonstrating a fundamental mechanical link between both these points.The analysis on the micro-seismicity during the evolutionary process of a rockfall in Mesnil-Val,France shows that it is basically feasible to take the characteristic AE event or the micro-seismicity as the indicator of the volume dilation point.