循环载荷下大试件岩石破坏声发射实验——岩石破坏前兆的研究

ACOUSTIC EMISSION EXPERIMENTAL RESEARCH ON LARGE-SCALED ROCK FAILURE UNDER CYCLING LOAD ——FRACTURE PRECURSOR OF ROCK

岩石等脆性材料在加载过程中,随着载荷的增加,材料内部的微裂纹产生、扩展并伴随着声发射现象的发生。声发射是研究脆性材料损伤演化的良好工具,它能连续、实时地监测脆性物体内部微裂纹的产生与扩展,这是其他任何方法都不具有的优势。在三轴应力条件下进行了大尺度岩石(片麻岩)破坏声发射实验,试件尺寸达1.05 m。为了模拟日、月潮汐力对地球的加载和卸载作用,在某一固定水平的轴向压力作用下,叠加上循环载荷。实验过程中记录到大量的声发射信息,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。利用声发射记录研究了预测岩石宏观破坏的 2 种前兆现象:能量加速释放及加卸载响应比剧增,为地震预测提供了实验依据。同时还发现,实验中存在声发射的 Felicity 效应。

The microfractures in a brittle material like rock may appear or grow while loading. Microfracturing process in a material results in energy dissipation and acoustic emission (AE). Acoustic emission is a good tool to detect the damage in brittle materials. Because it can monitor the microfractures in the body continuously and in-real-time and is better than other methods. Large-scaled gneiss failure experiments under triaxial loading are conducted. The size of the specimen reaches 1.05 m. In order to simulate the effect of tide-generating force of the sun and the moon, a cycle stress is loaded superposing on a basic axial load level. Lots of acoustic emission during the entire loading are recorded. The recording is able to indicate the occurrence time, location and magnitude of every damage (micro-crack) in the specimen. Acoustic emission record is used to study the two macroscopic failure precursors of rock, accelerating energy release (AER) and load/unload response ratio (LURR), which can be served as the experimental foundation of earthquake prediction. At the same time the Felicity effect is identified in the experiment.