基于重标极差分析的受载砂岩声发射特征研究

Research on acoustic emission characteristics of loaded sandstone based on R/S analysis

为了研究砂岩破坏过程中时间序列各个阶段声发射信号的响应规律,开展了砂岩单轴压缩试验。基于重标极差时间序列分析,得出了砂岩破坏过程中声发射计数时间序列的Hurst指数和分形维数。试验及分析结果表明,声发射信号与砂岩内部裂纹演化有很好的对应性;砂岩破坏的声发射信号时间序列遵循重标极差统计规律及分形规律,在时间序列的各个子区间内,Hurst指数值均大于1/2,呈现持久性,即随着时间的增加,产生的声发射信号呈现增长趋势;分形维数具有下降-上升-下降的特点,并在砂岩破坏时达到最低,这种变化趋势与砂岩内部微裂纹的发展情况一致。

In order to research response law of acoustic emission signal in various stages of time series during destruction process of sandstone,the uniaxial compression test of sandstone was carried out.The Hurst exponent and fractal dimension of the acoustic emission counting time series were obtained based on the R/S time series analysis.The results of test and analysis show that the acoustic emission signal has a good correspondence with the internal crack evolution of the sandstone.The time series of the acoustic emission signal of sandstone failure follows the R/S statistical law and fractal law.In the subintervals ofthe time series,the Hurst exponent is more than 1/2,showing persistent,that is,the resulting acoustic emission signal shows an increasing trend with the increase of time.The fractal dimension has the characteristics of falling-rising-falling and reaches the lowest at the time of sandstone failure.This trend is consistent with the development of micro-cracks in sandstone.