冻融作用下煤体孔隙结构损伤演化规律研究

Research on evolution law of coal pore structure damage under the action of freeze-thaw

为了揭示冻融作用对煤体孔隙结构的影响,采用冻融试验机对煤样进行冻融循环试验,利用声波测速仪和核磁共振设备对不同冻融循环次数下煤样的孔隙演化规律进行了分析。研究结果表明,冻融循环会造成煤体的孔隙结构损伤,促进煤体孔隙的发育,造成煤样波速降低,随着冻融循环次数的增加,煤样的小孔和中孔不断的扩展联通,造成煤样的大孔数量显著增加,孔隙连通性增强,煤样的总孔隙度、残余孔隙度和有效孔隙度和渗透率也随之增加,表明冻融循环能够提高煤层的透气性,从而有利于煤层气的抽采。

To reveal the effect of freeze-thaw on the pore structure of coal, a freeze-thaw test was carried out on the coal sample using a freeze-thaw machine. The pore evolution of coal samples under different freeze-thaw cycles was analyzed by using acoustic velocimeter and nuclear magnetic resonance equipment. The result shows that freeze-thaw can damage the pore structure and promote the development of pore of coal sample, and reduce the wave velocity of coal samples. With increase of freeze-thaw cycles, the micropore and mesopore of coal sample continue to expand and communicate, resulting in a significant increase in the number of macropore, the connectivity of pores, total porosity, residual porosity effective porosity and permeability of coal samples has increased, indicating that freeze-thaw can improve the permeability of coal seam, which is conducive to the extraction of coalbed methane.