帷幕体单轴压缩破裂声发射空间演化规律与分形特征研究

Spatial Evolution Rule of Acoustic Emission and Fractal Features of Fractures in Curtain Body Under Uniaxial Compression

基于岩石破裂声发射事件空间定位技术和分形几何理论,对以研山铁矿东帮砂砾卵石为骨料经胶结制作的帷幕体试块进行了单轴压缩试验研究,探讨了不同含水率下帷幕体试块的强度特性、AE事件累积计数特点、声发射事件空间演化规律及分形特征。研究结果表明:帷幕体试块破裂受到卵石骨料等成分的空间分布非均匀性影响和内部存在的各级结合缝控制,破裂空间分布呈现非均布向均布演化特征。一定的含水量可以提高帷幕体的强度;AE事件随应力增加逐渐活跃,其空间分布逐渐由区域中心向外扩散,渐呈均布趋势聚集于试件中部,且AE事件大部分产生于应力峰值前;AE事件空间分布分形维数随应力变化表现为先升维后降维,在峰值应力附近达到最大值,然后出现分维突降现象。分形维数降低可以作为预测帷幕体失稳破坏的前兆。

Based on spatial positioning technique and fractal geometry for acoustic emission event during rock crack growth,samples of curtain body that was cemented with sand and gravel from the east slope of Yanshan Iron Mine were taken for test under uniaxial compression. The strength characteristics, cumulative number of AE events, spatial evofution rule of AE event and fractal dimension of curtain body samples with different water contents were investigated. Results show that the rock fracture of curtain body was affected by non-uniform spatial distribution of gravel aggregate and the bonding joints at all levels inside the curtain body block,and the spatial distribution of fracture tended to evofve from non-uniformity to uniformity. It is found that a certain water content can increase the strength of curtain body. AE events gradually increases with the stress rising, and have spatial distribution spreading outward from the center of each area,tending to be uniform and gathering at the center of the block sample. Most of the AE events take place before the stress reaches the peak value. As for the spatial distribution of AE event, the fractal dimension finally decreases after an initial increase with the stress rising, reaching a maximum value with the stress around the peak value, which is foflowed by a sudden drop. It is concluded that the decreased fractal dimension can be regarded as a precursor for predicting a failure of curtain body.