1. State Key Laboratory Cultivation Base for Gas Geology and Gas Control,Henan Polytechnic University,Jiaozuo　 454000,China; 2. Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Coal Mines,Xiangtan　 411201,China; 3. School of Safety Science and Engineering,Henan Pol-ytechnic University,Jiaozuo　 454000,China; 4. The Collaborative Innovation Center of Coal Safety Production of Henan,Jiaozuo　 454000,China

为研究温度冲击下煤层微观结构的变化特征,采用高低温试验系统对原煤进行了温度冲击实验,利用扫描电镜、工业显微CT、压汞实验和低温液氮吸附实验对温度冲击前后煤的孔隙裂隙结构的演化发展进行了联合表征。基于数字图像处理技术,对温度冲击前后煤层扫描电镜图像进行二值化处理,定性与定量地分析了煤层的裂隙宽度变化,并统计分析了温度冲击前后煤层中孔隙的比表面积和孔径变化。研究结果表明:温度冲击作用促使煤样内部大孔之间相互贯通并形成宏观裂缝,导致大孔体积相应减少,中孔和小孔的体积均增大;温度冲击试验测试过程中所产生的最大热应力位于煤样表面的切向方向,温度冲击所产生的热应力超过煤样抗拉强度是导致裂隙萌生、扩展和相互贯通的直接原因。研究结果可为煤层气高效开发和提高煤层瓦斯抽采率提供技术支撑。

In order to study the change of microstructure of coal under temperature impact,the temperature impact ex- periment of coal was carried out by using high and low temperature test system. Scanning electron microscopy (SEM), industrial micro-CT,mercury injection experiments and cryogenic liquid nitrogen adsorption experiments were used to characterize the evolution of the pore fracture structure of coal before and after temperature shock. Based on digital im- age processing technology,the SEM images of coal reservoirs were binarized before and after temperature impact,and the fissure width variation of coal reservoirs was qualitatively and quantitatively analyzed. Also the specific surface area and pore size of pores in coal reservoirs were statistically analyzed before and after temperature shock. The results show that the temperature impact causes the large pores in the coal sample to penetrate each other and form macroscopic cracks,resulting in a corresponding decrease in the volume of macropores and an increase in the volume of mesopores and small pores. The maximum thermal stress generated during the temperature impact test is located in the tangential direction of the surface of the coal sample. The thermal stress generated by the temperature shock exceeds the tensile strength of the coal sample,which is the direct cause of crack initiation,expansion and mutual penetration. The re- search results can provide technical support for the efficient development of coalbed methane and the improvement of gas drainage rate in coal seams.

WANG Dengke,ZHANG Ping,LIU Shumin,et al. Experimental study on evolutionary characteristics of pore-fissure structure in coal seam under temperature impact[ J]. Journal of China Coal Society,2018,43(12):3395 -3403.