加卸荷条件下岩石力学特性与声发射特征

为了探究真三轴复杂应力变化条件下岩石强度及破坏模式，通过真三轴卸荷扰动测试系统对砂岩试件进行不同第二主应力加卸荷试验，讨论在加卸荷过程中岩石的力学特性及声发射特征。试验结果表明:第二主应力的增加对试件的承载能力起到先增强后弱化的效果；不同第二主应力加卸荷声发射能量及累计振铃计数变化趋势大体一致，耗散能量比在载荷达到岩石损伤强度时突增；声发射能量峰值提前于试件轴向应力跌落，声发射能量和累计振铃计数大幅突增可作为岩石破坏的前兆；在低载荷下岩石中活动主要是裂隙压密与发育，在达到岩石损伤强度后岩石中的活动主要是裂纹贯通形成破裂面，砂岩试件声发射定位点集中区域与试件主要破裂面基本吻合。

Mechanical properties and acoustic emission characteristics of rock under load unload condition

In order to explore the rock strength and failure mode under the condition of true triaxial complex stress change, different second principal stress load unload tests on sandstone specimens by true triaxial unloading disturbance test system was carried out, and the mechanical properties and acoustic emission characteristics of rocks during load unload process was discussed. The results show that the increase of the second principal stress has the effect of first strengthening and weakening the bearing capacity of the test specimen. The different second principal stress load unload acoustic emission energy and cumulative ringing count change trend is generally consistent. The dissipated energy is more sudden than when the load reaches the rock damage strength. The peak of acoustic emission energy is earlier than the axial stress drop of the test piece, and the sudden increase of the acoustic emission energy and the cumulative ringing count can be used as a precursor to rock damage. The activity in the rock under low load is mainly the fissure compaction and development. After reaching the rock damage strength, the activity in the rock is mainly the crack through to form the fracture surface. The concentrated area of the acoustic emission locating point of the sandstone specimen is basically consistent with the main rupture surface of the test piece.