Design and construction of a seismic physical model of room-pillar goafs in shallow coal seams
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摘要: 针对陕北浅埋煤层房柱式采空区探测精度不高的问题,制作地震物理模型进行浅埋煤层房柱式采空区物理模拟研究。按照物理模拟几何尺寸和波阻抗相似比原则设计地震物理模型;进行大量相似材料配比试验,确定低速黄土层相似材料为环氧树脂和硅橡胶(1∶1.2),泥岩相似材料为环氧树脂、硅橡胶和滑石粉(1∶0.2∶0.6),煤层为环氧树脂和硅橡胶(1∶0.4),泥质砂岩相似材料为环氧树脂和滑石粉(1∶0.8),砂岩为环氧树脂和滑石粉(1∶1.2);采用数控雕刻机雕刻煤层采空区及巷道保证高精度,利用浇筑法和粘接法相结合制作采空区夹心层及煤层倒扣浇筑的方法解决采空区巷道内留存空气的模型制作工艺难题,完成了房柱式采空巷道地震物理模型制作。经测量,物理模型的单层形态测量精度为0.2 mm、速度相对误差小于5 %、密度绝对误差为±0.3 g/cm3,满足模型设计要求。Abstract: In view of the problem of low detection accuracy of room-pillar goafs in shallow coal seams in northern Shaanxi, the seismic physical model is designed for physical simulation according to the principle of similarity ratio of geometry size and wave impedance. Through a large number of ratio tests of similar materials, the ratio of epoxy resin and silicone rubber is determined as 1 : 1.2 for similar materials of low velocity loess layer, 1 : 0.2 : 0.6 for epoxy resin, silicone rubber and talc for mudstone, 1 : 0.4 for epoxy resin and silicone rubber for coal seams, 1 : 0.8 for epoxy resin and talc for argillaceous sandstone, and 1 : 1.2 for epoxy resin and talc for sandstone. The numerical control engraving machine is used to carve the coal seam goaf and roadway to ensure high precision. By using the pouring method combined with the bonding method, the sandwich layer of goafs and coal seams is made to solve the problem of air model production in the goaf roadway, and the seismic physical model of the room-pillar goaf roadway is completed. The single-layer shape measurement accuracy of the physical model measures 0.2 mm, the speed relative error less than 5%, and the density absolute error ±0.3 g/cm3, which meets the design requirements of the model.
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表 1 实际地层和物理模型参数对比
Table 1 Parameters of the actual strata and the physical model
地层 层厚/m 纵波速度/(m·s–1) 密度/(g·cm–3) 实际 模型 黄土层 60 0.060 1 250 1.30 泥岩 42 0.042 2 400 2.20 上组煤 9 0.009 1 900 1.40 泥质砂岩 30 0.030 2 800 2.30 下组煤 5 0.005 1 950 1.45 砂岩 54 0.054 3 150 2.40 表 2 模型参数配比
Table 2 Parameter ratio table of the model
地层 材料 配比 纵波速度/(m·s–1) 密度/(g·cm–3) 转换密度/ (g·cm–3) 黄土层 A∶B 1∶1.2 1 305 1.08 1.620 泥岩 A∶B∶C 1∶0.2∶0.6 2 345 1.36 2.048 上组煤 A∶B 1∶0.45 1 920 1.11 1.635 泥质砂岩 A∶C 1∶0.8 2 816 1.54 2.313 下组煤 A∶B 1∶0.4 1 987 1.12 1.665 砂岩 A∶C 1∶1.2 3 000 1.66 2.496 -
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