煤体静载破坏微震、电磁辐射及裂纹扩展特征研究

为研究型煤在单轴压缩破裂过程中产生的微震、电磁辐射信号与裂纹演化特征的对应关系，利用自主设计的低噪声静态加载试验系统，对0～0.25、0.25～0.5、0.5～1.0、1～2 mm共4种不同粒度的型煤进行了单轴压缩破坏试验，同步采集了煤样破坏过程中的微震、电磁辐射信号及破坏视频图像，提出了一种煤体裂纹快速提取方法并计算了型煤裂纹面积的变化规律。研究结果表明：型煤在单轴压缩过程中产生的微震、电磁辐射信号及裂纹面积在时域上具有良好的同步性。型煤破坏过程中裂纹面积随时间变化曲线可分为4个阶段。第1阶段为压实阶段，煤样所受应力值较小，其表面的裂纹面积以极为缓慢的速率增加。第2阶段为初始破裂阶段，随着应力的增加和内部弹性势能的积聚，型煤表面裂纹面积的增加速率较压实阶段有明显提高，伴随产生许多细小裂纹。第3阶段为加速破裂阶段，随着应力继续增加以及材料内部积聚弹性能的释放，试样变形过程加速，导致裂纹面积增速进一步增大。第4阶段为卸压阶段，试样的裂纹面积达到最大值，承载能力急剧降低，发生失稳破坏。

Investigation on micro-seismic,electromagnetic radiation and crack propagation characteristics of coal under static loading

In order to study the correlation between micro-seismic, electromagnetic radiation signals and crack evolution characteristics of briquette under uniaxial compression loading, the failure experiments were carried out at four different range of particle sizes including 0–0.25 mm, 0.25–0.5 mm, 0.5–1.0 mm and 1–2 mm by means of self-designed and low-noise static loading experimental system. In addition, the micro-seismic, electromagnetic radiation signals and damage videos recorded during the failure of the briquette were collected synchronously. Based on the image semantic segmentation software, a fast crack extraction method on coal mass surfaces was proposed, and the variation law of crack area of briquette was calculated. The results show that the micro-seismic, electromagnetic radiation signals and crack area generated by briquette under the uniaxial compression process have a good correlation in the time domain. The curve of crack area with time in the process of briquette failure can be divided into four stages. In the first stage, the briquette is under compaction, the stress value is small, and the crack area on the surface increases at a very slow rate. In the second stage, with the increase of stress and the accumulation of internal elastic potential energy, the rate of increase of the surface area of the briquette is significantly higher than that of the first stage, accompanied by many fine cracks. In the third stage, as the stress continues to increase and the elastic energy is accumulated inside the material, the deformation process of the sample is accelerated, resulting in a further increase in the crack area. In the last stage, the crack area of the sample reaches its peak, the bearing capacity decreases sharply, the instability occurs, and the loading process ends.