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)

EXPERIMENTAL STUDY OF ROCK FAILURE PRECURSOR USING SIMULATED TIDE STRESS—LOAD/UNLOAD RESPONSE RATIO (LURR) AND ACCELERATING ENERGY RELEASE (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。

High LURR values and observations of Accelerating Moment/Energy Release （AMR/AER） prior to large earthquakes have suggested that intermediate-term earthquake prediction is possible. The LURR and AMR/AER have a similar physical origin. Experiments are very important in exploring the deformation and fracture of earth rock. Acoustic emission experiments of rock failure under triaxial stress have been conducted. The technique of acoustic emission is an important approach to reveal the micro-mechanism of deformation and failure of rocks. In order to simulate the rock in the earth crust the specimens were loaded by the combined action of a constant stress, intended to simulate tectonic loading, and a small sinusoidal disturbance stress, analogous to the Earth tide induced by the sun and the moon. Lots of acoustic emission during the entire loading was recorded. Each acoustic emission signal is characterized by the time, the three coordinates of the hypocenter and the amplitude, which is able to indicate the occurrence time, location and magnitude of every damage （micro-crack） in the specimen. In this paper LURR and AER are carded out in detail using the AE records. The results show that high LURR and AER occur before the macro fracture of the specimens. The experimental results confirm that LURR and AER are two macroscopic failure precursors of rock, which could be served as the experimental support of critical point hypothesis and foundation of earthquake prediction.