模拟引潮力作用下岩石破坏前兆的实验研究——加卸载响应比（LURR）理论和能量加速释放（AER）

大地震前加卸载响应比升高和能量加速释放这2种现象可以用来对地震进行中期预报。同时，加卸载响应比升高和能量加速释放有相同的物理机制。实验对于揭示地壳岩石的变形和破坏规律是非常重要的。在三轴应力条件下进行了岩石破坏声发射实验，声发射技术是研究岩石变形破坏微观机理的重要手段。为了模拟日月引潮力对地球的加载和卸载作用，在一常数加载率的轴向压力作用下，叠加上微小的正弦扰动，力求能够模拟地下岩石复杂的受力状态。实验过程中记录到大量的声发射信息，声发射记录包括声发射发生的时间、空间坐标和振幅，它能够反映岩石试件内部每一个损伤（微裂纹）发生的时间、地点和强度。利用声发射记录系统地分析了岩石试件破坏前能量释放及加卸载响应比的演化情况，结果显示，岩石试件宏观破坏前出现了能量加速释放及加卸载响应比剧增这2种前兆现象，从而对地震临界点理论给予了实验支持，同时也为地震预测提供了实验依据

Acoustic emission experiments of rock failure under load simulating the hypocenter condition

A series of acoustic emission (AE) experiments of rock failure have been conducted under cyclic load in tri-axial stress tests. To simulate the hypocenter condition the specimens are loaded by the combined action of a constant stress, intended to simulate the tectonic loading, and a small sinusoidal disturbance stress, analogous to the Earth tide induced by the Sun and the Moon. Each acoustic emission signal can indicate the occurrence time, location and relative magnitude of the damage (micro-crack) in the specimen. The experimental results verified some precursors such as LURR (Load/Unload Response Ratio) and AER (Accelerating Energy Release) before macro-fracture of the samples. A new parameter, the correlation between the AE and the load, has been proposed to describe the loading history. On the eve of some strong earthquakes the correlation between the Benioff strain and the Coulomb failure stress (CFS) decreases, similar to the variation of LURR prior to strong earthquakes