闪长岩单轴加载过程中声发射和弹性波速度变化规律的研究

为研究闪长岩在单轴加载过程中的声发射和各向波速变化规律,在单轴阶段加载和循环阶段加载条件下,对闪长岩岩样破裂过程中的声发射累计数、不同应力水平不同方向的波速、切线模量、轴向应变速率进行了研究。实验结果表明:(1)随着应力水平的增高,声发射事件数不断增加,在高应力水平(约80%峰值强度)时,声发射累计数急剧增多,随后切线模量出现震荡变化。(2)在加载过程中,压密程度及裂纹扩展方向对波速产生了巨大的影响,导致不同方向波速在不同的应力水平呈现出不同的变化规律,由此可以推测破裂面位置和破裂模式。在较高应力水平下(约60%峰值强度),平行于加载方向的波速趋于稳定,而垂直于加载方向的波速则持续下降,故用垂直于加载方向传播的波速预测岩石的破坏更具可靠性。(3)随着应力的增加,应变速率有逐渐减小的趋势,但临近岩石破裂时无异常变化出现,说明利用变形观测难以预测此类岩石的破坏。以上研究表明,根据纵波波速、声发射累计数和切线模量的变化可以有效预测岩石的破坏。

Research on the Variation of Acoustic Emission and Elastic Wave Velocity in Uniaxial Loading Process of Diorite

In order to have insight into the variation of acoustic emission and wave velocity in different directions during uniaxial loading process of diorite, the acoustic emission (AE) accumulative number, the wave velocity in different directions at different stress levels, the tangent modulus and the axial strain rate during fracture process of diorite under uniaxial stage loading and cyclic loading were experimentally studied, respectively. Results show: (1) AE event number increases with the increase of stress level, when stress level approaches to about 80% of peak strength, inflection point of accumulated AE curve appears, soon afterwards, tangent modulus fluctuates. (2) During loading process, the degree of compaction and the crack propagation direction have huge impact on wave velocity. The wave velocity in different directions shows different variations, based on which, it is possible to predict the rupture surface location and failure mode. At higher stress levels (about 60% of peak strength), the wave velocity horizontal to loading direction is tending towards stability, while the wave velocity perpendicular to loading direction continues to decline, so it is more reliable to predict rock failure by using wave velocity perpendicular to loading direction. (3) With the increase of stress level, strain rate presents decreasing trend, but doesn't show any abnormal behavior before rock failure, which indicates that it's difficult to predict rock failure by deformation observation. Above results show that rock failure can be effectively predicted by longitudinal wave velocity, acoustic emission accumulative number and tangent modulus variation.