侧向扰动下高应力岩石的声发射特性与破坏机制

ACOUSTIC EMISSION CHARACTERISTICS AND FAILURE MECHANISM OF HIGH-STRESSED ROCKS UNDER LATERAL DISTURBANCE

利用新研制的高应力岩石电液伺服扰动诱变试验系统,对100 mm×100 mm×100 mm大尺寸花岗岩试样进行不同静载作用下的侧向扰动破坏试验,同时利用PFC3D软件对其破坏机制进行分析。通过PCI–2型声发射系统监测发现:动力扰动下高应力岩石的声发射最大能量事件一般滞后于扰动峰值,发生在动力卸载段;随着静载的增加,声发射最大能量事件的发生时间有提前的趋势,而且较大能量事件数量增加。对试样进行基于弹性波速变化的损伤评价和声发射RA值(声发射撞击上升时间/幅度)的分析发现,不同静载下岩石的扰动破坏模式不同,较低静载时,扰动仅触发少量剪切裂纹并导致扰动近区岩石的局部剪切破坏;较高静载时,扰动同时触发剪切裂纹和拉伸裂纹,大量拉伸裂纹的出现最终导致岩石发生贯穿式整体溃崩破坏,基于数值模拟的机制分析也证实这点。

With newly-built experimental equipment,tests on 100 mm×100 mm×100 mm granite specimens under vertical static stresses with lateral disturbance have been conducted. Numerical simulation with software PFC 3D was used to reveal the inner mechanism of failure. The acoustic emission（AE） system PCI-2 was used to pick up AE signals. It′s found that the peak AE energy event usually happened at the unloading stage of the disturbance stress. The peak AE energy event tended to happen earlier and more frequently with the increase of the static stresses. Wave velocities at different positions were used to evaluate the damage distribution of the specimen at different loading conditions.RA values were also used to investigate the failure mechanism of specimens. When the static stress was low,only few shear cracks were triggered and a small shear failure zone was observed at the direct contact zone of the disturbance load. When the static stress was high,the shear cracks and the tensile cracks were both activated and the proliferation of tensile cracks resulted in the structural failure of specimens eventually. Numerical investigation also demonstrated this phenomenon.