1. National Engineering Research Center for Coal Gas Control,China University of Mining and Technology,Xuzhou　 221116,China;2. Faculty of Safety En-gineering,China University of Mining and Technology,Xuzhou　 221116,China;3. 5th Mine,Pingdingshan Tian’an Coal Co. ,Ltd. ,Pingdingshan　 467000, China;4. Chaili Mine,Shandong Energy,Zaozhuang Mining Group Co. ,Ltd. ,Zaozhuang　 277519,China

为解决深部近距离上保护层开采被保护层大量卸压瓦斯通过底板裂隙涌向首层采煤工作面极易造成瓦斯超限的问题,以平顶山天安煤业股份有限公司五矿为研究背景,采用理论分析、实验室实验、现场考察以及离散元数值模拟的手段,研究了深部近距离上保护层开采底板煤岩层裂隙瓦斯通道演化规律及下被保护层卸压瓦斯抽采时效性。研究表明:回采方向上底板煤岩层可分为原始应力区、卸压增透区和重新压实区,卸压增透区内煤体膨胀变形量大渗透率高,卸压瓦斯解吸扩散,底板采动裂隙使被保护层与采煤工作面贯通形成裂隙瓦斯通道。时间尺度上,卸压增透区的形成与上保护层回采到基本顶来压垮落时间段相对应,采动裂隙瓦斯通道伴随基本顶的破断垮落逐渐重新压实消失,卸压增透区范围在基本顶初次垮落前达最大值,回采推进期间与基本顶来压步距正相关。重新压实区域内煤岩层经历应力加载、卸荷、重新加载后可能出现损伤破坏,卸压瓦斯大量解吸引起煤体收缩变形,部分煤岩体受力比其原始应力更大出现压缩变形。卸压增透区是卸压瓦斯产生及运移的主要空间,也是进行卸压瓦斯拦截及抽采的高效区,瓦斯抽采工程需考虑采动裂隙演化的空间和时间效应。

In deeper underground short-distance upper protective seam extraction,substantial amounts of relief gas ab- sorbed in the protected coal seam would influx into the working face of the protective seam through the floor mining-in- duced fractures,which might cause gas concentration exceeding the statutory limit. This paper takes the 5th Mine of Ti- anan Coal Co. ,Ltd. as a case,and studies the floor fracture evolution and relief gas drainage timeliness in deep under- ground short-distance upper protective seam extraction,using the methods of theoretical analysis,laboratory test,field survey and 3D distinct element numerical simulation. It concludes that the floor area could be divided into initial stress region,pressure relived and permeability enhanced region ( PRPER),and re-compacted region. In the PRPER,the coal permeability enhancements was accompanied with its swelling,the mining-induced floor fracture became fracture gas channel connecting the protected coal seam to the protective working face. On the time scale,the PRPER occurred during the period between the initial extraction and the collapse of main roof. The fracture gas channel re-compacted and disappeared gradually with the collapse of main roof. During the normal excavation,the area of PRPER held a pos- itive correlation with the periodic weighting,and reached its peak when the preliminary extraction proceeded. In the re- compacted region,coal and rock stratum would suffer the stress of loading-unloading-reloading,generating certain dam- age and failure,and finally contribute to the gas desorption as well as the shrinkage of coal. The PRPER is the primary space that relief gas generates and migrates,and it is thus the target area for highly efficient relief gas drainage. When proceeding gas drainage projects,it is advised to consider the effect of the time-space on the fracture evolution induced by mining.

国家重点基础研究发展计划(973)资助项目(2011CB201204)；国家自然科学基金面上基金资助项目(51374204；51474212)；

Wang Wei,Cheng Yuanping,Yuan Liang,et al. Floor fracture evolution and relief gas drainage timeliness in deeper underground short-dis- tance upper protective coal seam extraction[J]. Journal of China Coal Society,2016,41(1):138-148.