不同温度下褐煤裂隙演化的显微CT试验研究

利用显微CT系统直观地研究褐煤从20℃～600℃裂纹的演化扩展过程,对原生裂纹和新生微裂纹的扩展演化进行详细的分析研究。研究结果表明:20℃～100℃,褐煤热破裂程度中等,只有很少的微裂纹产生;100℃～300℃热破裂剧烈,原生裂纹扩展延伸,且产生许多微裂纹,新旧裂纹扩展、延伸、搭接形成裂隙网络;300℃～500℃裂纹的扩展很缓慢;500℃～600℃,裂纹有闭合的趋势。随温度升高,微裂纹易沿层理方向产生于软煤质中,止裂于硬质带边缘,部分垂直层理方向的裂纹会在硬质带边缘分叉后沿层理方向扩展,裂纹沿层理方向的扩展速度远大于垂直层理方向的。

MICRO-CT EXPERIMENTAL STUDY OF CRACK EVOLUTION OF LIGNITE UNDER DIFFERENT TEMPERATURES

The crack evolution of lignite from 20 ℃ to 600 ℃ is studied by using micro-CT system intuitively. The extension and evolution of original cracks and new microcracks are discussed in detail. The study results show as follows：(1) From 20 ℃ to 100 ℃，thermal cracking degree of lignite is moderate and just a few new microcracks initiate. (2) From 100 ℃ to 300 ℃，thermal cracking is acute；many new microcracks initiate and original cracks extend quickly. The original and new cracks spread，overlap and connect with each other and finally form a crack network. (3) From 300 ℃ to 500 ℃，the extension of microcrack is very slowly. (4) From 500 ℃ to 600 ℃，some microcracks have trend of closure. With the increase in temperature，the microcracks initiate in soft coal along the bedding of coal seam and are arrested to hard coal；some cracks perpendicular to bedding direction will split on the edge of hard coal layer and then extend along the bedding of coal seam. The extension rate of cracks parallel to bedding direction is greater than that perpendicular to bedding direction.