液氮冷冲击时长对煤体致裂效果的影响  

The influence of cold shock duration of liquid nitrogen on the fracturing effect of coal

作　　者：魏则宁 翟成[1,2,3] 孙勇[1,2,3] 丛钰洲[1,2,3] 唐伟 WEI Zening;ZHAI Cheng;SUN Yong;CONG Yuzhou;TANG Wei(School of Safety Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;National Engineering Research Center for Coal Mine Gas Control,Xuzhou,Jiangsu 221116,China;Key Laboratory of Coal Methane and Fire Control,Ministry of Education,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)

机构地区：[1]中国矿业大学安全工程学院,江苏徐州221116 [2]煤矿瓦斯治理国家工程研究中心,江苏徐州221116 [3]中国矿业大学煤矿瓦斯与火灾防治教育部重点实验室,江苏徐州221116

出　　处：《中国矿业大学学报》2022年第2期273-282,共10页Journal of China University of Mining & Technology

基　　金：国家杰出青年科学基金项目(51925404);国家自然科学基金项目(51774278)。

摘　　要：注氮参量的设置与煤体致裂效果密切相关,为研究液氮冷冲击循环过程中不同冷冲击时长对致裂效果的影响,开展不同冷冲击时长(5,10,15,20 min)液氮溶浸试验,利用低场核磁共振设备对比分析各组煤样孔径分布、孔隙数量、孔隙度及吸附/渗流孔变化规律,进而表征煤样在不同冷冲击时长下的孔隙发育程度.研究表明:不同冷冲击时长下煤体孔隙特征演化过程具有明显的差异性.不同冷冲击时长下中大孔的变化率表现出前期快速增长、后期缓慢增长的现象;冷冲击时长与孔隙度参数变化率、吸附孔和渗流孔占比变化率均呈现指数相关关系,具有“前期增长快速,后期增长平缓”的特点.不同冷冲击时长下的液氮循环溶浸处理本质上是温度在不同时间尺度上的循环.对冷冲击时长的控制是基于煤体内部温度降的变化,以期实现更好的热应力致裂作用效果,提高瓦斯抽采效率.该研究对现场循环注氮致裂的冷冲击时长选择具有一定的指导意义.The setting of nitrogen injection parameters is closely related to the fracturing effect of coal.In order to study the influence of different time length on the fracturing effect during the liquid nitrogen cold shock cycles,the liquid nitrogen immersion experiments with different cold shock duration(5,10,15,20 min)were carried out.The pore size distribution,pore number,porosity and adsorption/seepage pore variation of coal samples in each group were analyzed by low-field nuclear magnetic resonance equipment,and the pore development degree of coal samples under different cold shock duration was characterized.The results show that the evolution process of coal pore characteristics is obviously different under different cold shock duration.The change rate of the mesopores and macropores shows rapid growth in the early stage and slow growth in the late stage under different cold shock duration.The cold shock duration is exponentially correlated with the change rate of porosity parameters and the change rate of the proportion of adsorption and seepage pores,which is characterized by“rapid growth in the early stage and slow growth in the late stage”.The liquid nitrogen immersion treatment under different cold shock duration is essentially the alternating temperature cyclic change on different time scales.The control of the cold shock duration is based on the change of the temperature drop of the internal coal,with a view to achieve better thermal stress cracking effect and improve the efficiency of gas extraction.This study has a certain guiding significance for the selection of the cold shock duration of in-situ cyclic nitrogen injection.

关 键 词：冷冲击时长 液氮致裂 孔隙结构 核磁共振 热应力 

分 类 号：TD712[矿业工程—矿井通风与安全]