基于波速场成像技术的岩石损伤评价研究

Rock damage evaluation based on wave velocity field imaging technology

基于区域相关性的声发射波速场成像技术,开展岩石破裂过程的声发射探伤成像实验,从损伤状态探测的准确程度和岩石损伤演化过程两方面对波速成像进行检验,构建基于波速场的损伤评价体系,确立基于声发射波速场的损伤变量。研究结果表明:波速成像云图以区域化的形式准确反演损伤区域的空间位置,低波速周边的弱化区域能够表征裂纹未来发育方向,高、低波速区域的离散分布刻画了岩石真实状态。波速成像云图的演化过程揭示了岩石关键破裂损伤多发生于波速异常区域或异常区域交界处,并以此为核心低波速区域不断聚集、扩展,向整体贯通的破坏机制。经过"波速场特征提取-综合权重确定-TOPSIS法综合评价"对岩石损伤状态进行评价,在分级加载过程中,岩石经历了损伤稳定发展与损伤加速上升的过程,在加速上升期间存在裂纹压密使损伤短暂降低的现象。该评价方法对岩石的微破裂行为刻画效果显著,能够在定量化描述损伤状态的同时显现损伤分布区域,对岩石损伤稳定性评价具有重要意义。

Based on acoustic emission regional wave velocity imaging technology,acoustic emission detection experiments in the process of rock cracking were carried out. The effect of acoustic emission wave velocity imaging technology was examined in terms of the accuracy of damage state detection and the process of rock damage evolution. A damage evaluation system was constructed and a damage variable related to acoustic emission wave velocity field was established. The results show that the spatial location of the damaged area can be accurately described by the regionalization of the velocity imaging nephogram. The weakening area around the low wave velocity can represent the future development direction of cracks. The discrete distribution of high and low wave velocities can depict the real state of rocks. The evolution process of the nephogram reveals that the key fracture damage of rocks occurs mostly at abnormal areas of the wave velocity or their junctions and,around them,the low wave velocity area gathers,expands and penetrates into the whole rock. An evaluation system of feature extraction,determination of weight and comprehensive evaluation by TOPSIS method was proposed for assessing the damage state of rocks. It is also shown that,under multi-stage loading,the rock undergoes a stable and accelerated damage development and that the damage decreases temporarily due to crack compaction in the stage of the accelerated damage development. This evaluation method,which can quantitatively describe the damage state and show the damage distribution area at the same time,has a remarkable effect on the characterization of micro-fracture behavior and great significance for the evaluation of rock damage state.