A study on the effective extraction layer of overburden fracture zone in goaf based on key layer theory
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摘要:
采空区覆岩断裂带有效抽采层位是布置高位抽采钻孔治理邻近层和采空区瓦斯的基础。基于关键层理论,建立了断裂带有效抽采层位数学模型,确定了有效抽采层位上下边界:有效抽采层位的下边界为采空区垮落带之上的第1层关键层,上边界为采空区上覆岩层高度为10倍采高以下的第1层关键层,有效抽采层位包含下边界岩层,不包含上边界岩层。根据断裂带有效抽采层位数学模型计算得出段王煤矿8+9号煤层断裂带有效抽采层位为煤层顶板上方12.6 m处的中砂岩到39.3 m处的4号煤;根据采空区覆岩断裂带钻孔窥视结果,得出工作面断裂角约为62°,破断断裂带高度范围为煤层顶板上方11.5~40.5 m区域。在段王煤矿进行高位钻孔抽采试验,得出实际的断裂带有效抽采层位为煤层顶板上方13.9 m处的中砂岩到37.4 m处的砂质泥岩。钻孔窥视分析和高位钻孔抽采试验结果均验证了断裂带有效抽采层位数学模型的准确性,研究成果可为高瓦斯和煤与瓦斯突出矿井的高位抽采工程设计提供理论依据。
Abstract:The effective extraction layer of the overburden fracture zone in goaf is the basis for arranging high-level extraction boreholes to treat adjacent layers and gas in goaf. Based on the key layer theory, a mathematical model for the effective extraction layer in fracture zones is established, and the upper and lower boundaries of the effective extraction layer are determined. The lower boundary of the effective extraction layer is the first key layer above the collapse zone of the goaf, and the upper boundary is the first key layer below 10 times the mining height of the overburden layer in the goaf. The effective extraction layer includes the lower boundary rock layer and does not include the upper boundary rock layer. According to the mathematical model of the effective extraction layer of the fracture zone, it is calculated that the effective extraction layer of the fracture zone in the 8+9 coal seam of Duanwang Coal Mine is from the medium sandstone at 12.6 m above the coal seam roof to the No. 4 coal at 39.3 m. According to the drilling and observation results of the overburden fracture zone in the goaf, the fracture angle of the working face is about 62°. The height range of the fracture zone is 11.5-40.5 m above the coal seam roof. A high-level drilling and extraction test is conducted at Duanwang Coal Mine. It is found that the actual effective extraction layer of the fracture zone is from medium sandstone at 13.9 m above the coal seam roof to sandy mudstone at 37.4 m. The results of drilling observation analysis and high-level drilling extraction test have verified the accuracy of the mathematical model of effective extraction layer in the fracture zone. The research results can provide theoretical basis for the design of high-level extraction engineering in high gas and coal and gas outburst mines.
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表 1 工作面采空区覆岩关键层判别结果
Table 1. Identification results of key layer of overburden in goaf of working face
层号 层厚/ m 密度/
(kg·m−3)抗拉强度/
MPa弹性模量/
GPa岩层岩性 关键层位置 1 4.40 1 300 0.3 3 8+9号煤 — 2 8.44 2 300 0.5 5 砂质泥岩 — 3 13.19 2 400 3.0 8 中砂岩 关键层 4 0.50 2 300 0.5 5 泥岩 — 5 0.76 1 300 0.3 3 6号煤 — 6 4.83 2 300 0.5 5 砂质泥岩 — 7 3.80 2 500 2.0 9 细粒砂岩 关键层 8 0.21 2 300 0.5 5 泥岩 — 9 0.58 1 300 0.3 3 5号煤 — 10 6.39 2 300 0.5 5 砂质泥岩 — 11 0.60 1 300 0.3 3 4号煤 — 12 4.89 2 500 2.0 9 细粒砂岩 关键层 13 1.50 2 300 0.5 5 砂质泥岩 — 表 2 钻孔主要参数
Table 2. Main parameters of borehole
钻孔编号 方位角/(°) 倾角/(°) 终孔深度/m 1 0 30 30 2 0 40 70 -
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