Development af AE detection system in rock masses

岩体破坏预测对岩石开挖设计和地下洞室稳定性控制具有重要意义。为此，对大岛花岗岩单轴蠕变过程中声发射事件的时间序列进行了研究。利用微型计算机乌奇普系统同时测量声发射事件的发震时间和震级，首先对声发射事件的发生进行了图解分析。显然，没有地震时观察到的烈性地震序列。其次，在连续事件之间的时间间隔内检验声发射事件的发生是否是泊松过程。通过x^2检验对其进行检验。试验表明，在二次蠕变过程中，声发射事件的发生是一个与其大小无关的泊松过程。在第三纪蠕变阶段，除灾变迫在眉睫外，大的声发射事件的发生是泊松过程，而较小的声发射事件的发生则从泊松过程开始发展。为了预测未来的不稳定性，尝试了通过在威布尔概率尺度上绘制大型声发射事件的时间间隔分布的分析。利用所获得的知识，可以在不久的将来建立实用的岩体声发射探测系统。

The prediction of failure in rock masses in most important to design the excavation of rocks and to control the stability of underground openings. For the fundamental experiment of this purpose, time series fo acousitc emission (AE) events during uniaxial creep in Oshima granite were investigated. Both the origin time and the magnitude of AE events were measured simultanenously; by using the mictocomputer wuqipped system.First, the occurrence of AE events was analized graphically. Apparently, ther were no afrershock sequence which are observed with earthquakes. Second, whether the occurrence of AE events is a poisson process of not was examined at time intervals berween consecutive events. It was also tested by means of the x^2-test. The test shows that during the secondary creep the occurrence of AE events is a poission process unrelated to their magnitude. During the stage of tertiary creep, while the occurrenece of large AE events was a Poisson process except when the catastrophe was imminent, the occurrentce of smaller AE events began to deveate from the poisson process. To predict forthcoming instability, the analysis on the time-interval distribution of large AE events by plotting them on a Weibull probability scale was tried. The AE occurrence changed from being random to being periodic just prior to the main fracture.By using the obtained knowldge, the useful AE detection system in rock masses would be constructed in the near future.