摘要
为了研究不同饱水度煤体在液态CO_(2)冻融作用下孔隙裂隙的演化特性,利用自主研发的液态CO_(2)冻融试验系统预处理煤样,采用核磁共振仪(NMR)探究液态CO_(2)冻融前后煤样的t_(2)谱分布、孔隙体积、孔隙度及t_(2)截止值演化特性。结果表明:液态CO_(2)冻融作用能促进煤样内部孔隙结构发育,使煤样中微小孔、中孔和大孔数量均增多;煤样饱水度对液态CO_(2)冻融煤致裂效果影响显著,随煤样饱水度增大,煤样总孔隙体积增大幅度呈直线增长趋势,煤样总孔隙度及有效孔隙度增长幅度呈直线形增长,而残余孔隙度增长幅度呈直线形下降,且完全饱水煤样总孔隙体积、总孔隙度和有效孔隙度分别是干燥煤样的2.48倍、2.49倍和2.56倍,t_(2)截止值从0.38 ms逐渐减小至0.30 ms,煤体内流体流动的自由空间增大,即有效孔隙体积逐渐增大,液态CO_(2)冻融有利于提高煤体的渗透性。
To study the evolution of pores and fissures of different saturated coal bodies under the action of liquid CO_(2) freezing and thawing,the self-developed liquid CO_(2) freezing and thawing test system was used to pretreat the coal samples,and nuclear magnetic resonance(NMR)was used to study the t2 spectrum distribution,pore-volume,porosity and t_(2) cut-off evolution law of coal samples before and after the freezing and thawing of liquid CO_(2).The study shows that:in the t_(2) spectrum,the t_(2) curve of the coal sample after freezing with liquid CO_(2) shifts upwards while the number of micropores,mesopores and macropores increase,indicating that the freezing and thawing of liquid CO_(2) can promote the development of the internal pore structure of the coal sample.Coal saturation has a significant impact on the cracking effect of liquid CO_(2) freeze-thaw coal.With the increase of coal saturation,the total pore and adsorption pore volume of the coal increases linearly,and the seepage pore volume increases exponentially.Besides,the increase rates of the total porosity and the effective porosity of the coal sample increase linearly,while that of the residual porosity decreases linearly.The total pore volume,total porosity,and effective porosity of the fully saturated coal sample are 2.48 times,2.49 times,and 2.56 times those of dry coal samples.The t_(2) cut-off value gradually decreases from 0.38 ms to 0.30 ms.The number of channels for free fluid flow continues to increase.There is an extension and penetration between pores and cracks of different sizes,which ultimately promotes the coal body.The complexity of the internal fracture network continues to increase,and the effective pore volume gradually increases.The freezing and thawing of liquid CO_(2) are beneficial to improve the permeability of coal.
作者
周西华
周露函
白刚
苗春颖
ZHOU Xi-hua;ZHOU Lu-han;BAI Gang;MIAO Chun-ying(School of Safety Science and Engineering,Liaoning Technical University,Huludao 125000,Liaoning,China;Ministry of Education Key Laboratory of Mine Thermal Disasters and Prevention,Liaoning Technical University,Fuxin 123000,Liaoning,China)
出处
《安全与环境学报》
CAS
CSCD
北大核心
2022年第5期2474-2481,共8页
Journal of Safety and Environment
基金
辽宁省教育厅青年项目(LJ2019QL002)
辽宁工程技术大学学科创新团队项目(LNTU20TD-29)。
关键词
安全工程
饱水度
液态二氧化碳
冻融
孔隙结构
孔隙度
safety engineering
water saturation
liquid CO_(2)
freeze-thaw
pore structure
porosity
作者简介
周西华,教授,博士,从事矿山安全、煤矿火灾与瓦斯高温防治等研究,xihua_zhou68@163.com。
