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通过对三种岩石试样进行单轴循环加载试验,获得岩石试样加载过程中声发射事件率、能量率和空间位置分布数据。运用相空间重构理论直接从时间序列上通过G-P算法求得事件率和能量率关联分维,根据柱覆盖法求解得到声发射事件源空间分布关联分维。研究结果表明,声发射事件率、能量率和空间分布都具有分形特性,且声发射源空间分布分形特性最为显著。相空间的选取对关联维数有一定影响,相空间取值为4时能够较好地计算关联维数。将不同加卸载循环声发射源空间分布的变化趋势和声发射源空间分布关联维数变化趋势进行对比发现,声发射关联维数能够很好地反映岩石内部损伤破坏的发展。在等压加卸载条件下,声发射源空间分布关联维数显著突增。随着加卸载循环应力的增加,关联维数总体呈下降趋势,在达到较高应力时,关联维数则在较小区间内波动或下降趋势变得极其缓慢。该特点可以作为矿山地压微震监测预警的参考依据。
Through the uniaxial cyclic loading tests of three kinds of rock samples, the acoustic emission event rate, energy rate and spatial position distribution data of the rock samples were obtained. The correlation fractal dimension of event rate and energy rate was obtained by G-P algorithm directly from time series using the theory of phase space reconstruction. The spatial fractal dimension of acoustic emission event source was obtained by solving the column coverage method. The results show that the acoustic emission event rate, energy rate and spatial distribution have fractal characteristics, and the spatial distribution of acoustic emission sources is the most significant. The selection of phase space has a certain influence on the correlation dimension. When the phase space value is 4, the correlation dimension can be well calculated. Comparing the trend of spatial distribution of different AE sources with that of AE sources, we find that the correlation dimension of acoustic emission can well reflect the development of damage damage in rock. Under the conditions of isobaric loading and unloading, the correlation dimension of the spatial distribution of acoustic emission sources significantly increases. With the increase of loading-unloading cycle stress, the correlation dimension generally declines, and when the higher stress is reached, the correlation dimension fluctuates or declines more slowly in the smaller interval. This feature can be used as a reference for mine ground pressure microseismic monitoring and early warning.