针对中国神东矿区浅埋近距离双厚煤层开采的工程实际,建立三维物理相似模型、PFC2D数值模型和理论模型,对双厚煤层开采后的覆岩裂隙发育规律进行研究。综合研究表明:上煤层开采后,裂隙带发育高度约为55.5～60.3 m,而下煤层推进约60 m,层间关键层初次断裂,引起上、下采空区连通,并在主关键层断裂以后形成的裂隙直达地表,高度约为146.5～153 m;采动空隙场呈"双拱"形态,并结合关键层理论,将覆岩划分为不规则空隙带和周期性空隙带,以及拱间优势空隙带和拱下微空隙带;提出了近距离双煤层开采综合采厚的计算方法,结合修正的综放开采裂隙带发育高度预计公式,可进行近距离双厚煤层裂隙带发育高度计算。研究成果揭示了浅埋双厚煤层开采后地表-上采区-下采区的漏风机制,并根据采动空隙场分布特点提出了堵风治燃的工程对策,可为类似矿井的防灭火提供借鉴。

Three models including three-dimensional physical model,PFC2D numerical model,and theoretical model were established for the shallow double-thick coal seams in Shendong mining area in China. The development rule of o- verburden fractures after double coal seams excavation was studied. The results show that the height of fractured zone is about 55. 5-60. 3 m after upper seam excavation. The key stratum between two seams is first fractured resulting in the connectivity of upper and lower gobs when advance distance of working face was 60 m. After that,the main key stratum is fractured,and the fractures extends to surface. The ultima height of fractured zone is about 146. 5-153 m. The ends of gob with higher porosity is taken as a dominant pathway of air flow,as the compaction degree of gangue at there is more than that at the middle of gob with lower porosity. Mining-void field presents a double-arc shape,com- bined with the theory of key stratum,overburden strata can be divided into irregular void zone,periodic void zone, dominant void zone between arcs,and micro void zone under arc. Engineering values of these void zones are also illus- trated in detail. A method is proposed for calculating the equivalent mining height of close double coal seam mining. And it is used in predicting the height of fracture zone combined with modified predicting formula of top coal caving.In conclusion,the study reveals the air leakage mechanism of surface-upper mining section-lower mining section in shallow double-thick coal seams mining. The engineering measures for air leakage and spontaneous combustion are also put forward according to the characteristics of void field. It could provide a reference for other similar coal mines in the actual operations of fire prevention and extinguishment.