顶板岩石失稳破坏电位临界慢化特征实验研究

Experimental study on electric potential critical slowing down characteristics before unstable failure of roof rocks

为研究顶板岩石失稳破坏过程中表面电位信号的临界慢化特征,对顶板岩样进行了受载破坏实验,测试并采集了岩样受载过程中的表面电位信号。运用临界慢化理论计算并分析了电位信号-时间序列的方差和自相关系数。结果表明,岩样受载破坏过程中的表面电位变化与载荷及应变具有良好的对应关系;岩样受载过程中的表面电位信号存在临界慢化现象,电位信号的方差和自相关系数在岩样主破裂前均出现了急剧增大并持续增加的趋势,可作为预示岩样破坏的前兆信号;不同的窗口长度、滞后步长对表征电位信号临界慢化现象的自相关系数、方差的稳定性及变化趋势有影响;方差相比于自相关系数,更能有效预示岩样趋于失稳破坏的临界点。

In order to study critical slowing down characteristics of surface electric potential(EP)before unstable failure of roof rocks,loading failure experiment of rock specimens was carried out,the surface EP signal of rocks was collected in loading process.Based on theory of critical slowing down,variance and autocorrelation coefficient of the potential signal time sequence were calculated and analyzed.The analysis results are as follows:there is a good correspondence between the change of surface potential,the load and strain during the whole loading process;EP signal of rock has the phenomenon of critical slowing down in the loading process,the variance and autocorrelation coefficient of EP has sudden increase and continuously increasing trend before the main rupture,it can be used as a precursory signal to indicate unstable failure of rocks;the different window lengths and lagging steps affect the volatility stability and variation tendency of autocorrelation coefficient and variance of EP signal;compared with autocorrelation coefficient,variance is more effective for prediction of the critical failure point of the rock specimens.