单轴应力作用下花岗岩的稳定蠕变过程中声发射发生的自激过程

通过实验室的试验,发现了声发射(AE)时空分布的丛集现象。为了研究声发射发生的随机过程,测出了在不同应力水平下处于稳定蠕变阶段的声发射事件发生的时间。大岛花岗岩受不同强度的恒定单轴应力的持续作用。声发射事件的发生时间被分为油松过程和自激过程两部分;在后一过程中,前一个事件会激发下一个事件。应力越大源分布越集中,裂隙密度越大,自激发特性越强,这与在较高应力水平下源分布越集中的情况相符。

原地地应力状态和岩石强度对流体诱发地震活动影响的实验室研究

在水渗入干燥和饱和的花岗岩样品过程中,我们观测到了声发射现象和P波速度变化,以此来研究流体诱发地震活动机制。在流体静压力和高偏应力作用下,分别均匀地将水注入干燥和饱和的圆柱体花岗岩端部表面中,用计算机层析技术揭示的二维P波剖面图显示出水前缘皆平行于端部表面,而且在流体静压力作用下,水前缘均匀地离开干燥花岗岩的端部表面。在水注入饱和花岗岩期间,由于受到差应力的作用,岩石内部产生了大量的诱发微裂纹,而对干燥花岗岩却没有产生。声发射源的位置和表面体应变分布显示出诱发微裂纹发生于局部破裂强度较弱的区域。由地下流体流动或水压变化触发的地震活动受控于围岩中既存的原地差应力状态和岩石强度分布。

Effect of Rock Structure on Statistical Characteristics of Acoustic Emission

A comparative study on acoustic emission during deformation of two kinds of granites with different structures under triaxial compression was performed using a new acoustic emission recording system with full-waveform record and broad-dynamic range. One is the Inada aplite-granite of homogeneous structure from Japan and the other is the Mayet granite with cemented natural joints from France. For the former granite, acoustic emission events are dispersed randomly and there is no clear clustering along the major fracture. For the latter granite, acoustic emission events are mainly concentrated near the joints. Acoustic emission events occur synchronously with the volumetric dilatation in the former one but far earlier than the volumetric dilatation in the latter one. The two kinds of granites are also clearly different in the frequency spectrum of acoustic emission. The former has a narrower frequency band and a higher frequency component, whereas the latter has a wider frequency band and generally a