基于单键群方法的岩石破裂声发射时空分布特征的试验研究

 基于声发射定位技术和单键群方法，对在单轴压缩条件下岩石破裂过程中的声发射空间相关长度的变化特征进行试验研究。利用单键群构架的键长分布对声发射事件进行分色，可定量确定声发射事件集中程度。研究结果表明：基于单键群方法，影响声发射空间相关长度变化的因素有2个，一是应力的释放导致空间相关长度的下降；二是应力场的转移导致空间相关长度的增长。根据声发射空间相关长度变化的不同，可将岩石岩样分为3种类型：(1) 破坏前无明显塑性变形阶段的岩石岩样，空间相关长度呈现以幂律为特征的加速增长态势，且在岩石破坏前达到最大值；(2) 对于破坏前有明显塑性变形阶段的岩石岩样，在塑性变形阶段，应力场的转移和岩石内部局部塑性2种因素的影响使得空间相关出现或增长或下降的波动现象；(3) 对于加载过程中出现明显局部裂纹的岩样，局部破裂会导致声发射事件群集，致使空间长度减小，但是对于岩石整个破坏过程，空间相关长度呈现整体的增长趋势。单键群构架的键数具有分形特征，其反映的声发射事件的空间演化特征与空间相关长度所反映的情况一致。空间相关长度的增长反映了岩石内部应力场的长程转移过程。在塑性变形阶段，空间相关长度与之前阶段变化的差异对于预测岩石的破坏具有重要意义。

EXPERIMENTAL STUDY OF TEMPORAL AND SPATIAL DISTRIBUTION CHARACTERISTICS OF ACOUSTIC EMISSION DURING ROCK FRACTURE BASED ON SINGLE-LINK CLUSTER METHOD

Based on acoustic emission(AE) locating technique and single-link cluster(SLC) method，the experimental study of change characteristic of spatial correlation length of AE events during the fracture process of rock specimens under uniaxial compression is conducted. The color separation of AE events by link¢s length distribution of SLC frame can be used to study the cluster concentration degree of AE events. The results show that the two factors influencing the change in spatial correlation length are as follows：stress release，which leads correlation length to decrease，and stress field transferring，which leads correlation length to increase. According to the changes in spatial correlation length，the rock specimens can be classified into three types：(1) the specimens show no significant plastic deformation before failure. The spatial correlation length of AE events present a trend of accelerate growth which features as power law. It reaches the maximum value before rock failure. (2) The specimens show remarkable plastic deformation before failure. In plastic deformation stage，the spatial correlation length can either increase or decrease which depends on combination of the two above mentioned factors. (3) The specimens show clear cracking localization during loading. The spatial correlation length shows a sharp decrease when macro cracks generate. The link¢s count in SLC frame shows fractal characteristics. It can reflect the spatial evolutional process of AE events，which is consistent with the results acquired by spatial correlation length. The increase in spatial correlation length reflects the long-range transfer of stress field process. The difference between spatial correlation length and its previous value during the plastic phase has important significance for predicting rock failure.