Regularity and control of overburden and surface fractures in shallow-contiguous seams
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摘要: 我国西部神府东胜煤田主要赋存浅埋近距煤层,煤层埋藏浅,覆岩上部厚松散层大范围分布,近距煤层开采导致覆岩与地表裂缝发育严重,加剧了原本脆弱的生态环境进一步恶化。为探究浅埋近距煤层开采覆岩与地表采动裂缝发育规律,掌握其控制方法,以柠条塔煤矿1-2煤层和2-2煤层开采为背景,结合实测统计分析、物理模拟和分形理论,掌握浅埋顶部单一煤层开采和重复采动下覆岩与地表裂缝发育特征,揭示煤柱布置对裂缝发育的控制作用。研究表明,煤层开采导致的地表裂缝可分为平行于工作面的动态裂缝和工作面开采边界地表裂缝(切眼边界侧地表裂缝和区段煤柱侧地表裂缝),动态裂缝在开采后能够实现自修复,工作面开采边界的地表裂缝不能自修复。下煤层开采区段煤柱侧覆岩与地表采动裂缝发育严重,其与区段煤柱错距密切相关。1-2煤层开采后,基岩垮落角为60°,土层垮落角为65°,边界煤柱侧地表裂缝的宽度为0.26 m。下部2-2煤层开采,煤柱叠置、错距20、40 m时,区段煤柱侧覆岩采动裂缝宽度分别为0.81、0.45和0.22 m,地表裂缝宽度分别为0.65、0.30和0.12 m。通过确定合理煤柱布置方式,能够有效控制覆岩和地表采动裂缝的发育程度,据此确定柠条塔煤矿1-2煤层和2-2煤层开采的合理煤柱错距应大于40 m。Abstract: The Shenfu-Dongsheng Coalfield in western country mainly occurs in shallow close multi-seam, and the thick loose layers on the overlying rock are distributed in a wide range. Mining in shallow-contiguous seams results in serious development of overlying rock and surface fractures, which aggravates the deterioration of the originally fragile ecological environment. In order to explore the mining-induced overburden and surface fractures development characteristics in shallow shallow-contiguous seams, and obtain its control method. Taking No.1-2 seam and No.2-2 seam mining in Ningtiaota Coal Mine as background, this paper obtains the development characteristics of fractures in shallow single seam mining and repeated mining through in-site statistic analysis, physical simulation and fractal theory. Besides, the control effect of pillar staggered distance to mining-induced fractures is revealed. The results show that the mining-induced surface fractures can be divided into two types, one is dynamic fractures which are parallel to the working face, and another is mining boundary surface fractures which contain open-off boundary surface fractures and pillar boundary surface fractures. The dynamic fractures can realize self-repairing after mining, while the mining boundary surface fractures can not realize self-repairing. After lower seam mining, the pillar boundary overburden and surface fractures development seriously, which are closely related to pillar staggered distance. After No.1-2 seam mining, the bedrock caving angle is 60°, and the soil layer caving angle is 65°, the width of surface fracture along coal pillar, 0.26 m. After lower No.2-2 seam mining, when the pillars are aligned, with pillar staggered distance of 20 m and 40 m, the width of overburden fractures are 0.81 m, 0.45 m and 0.22 m respectively, and the width of surface fractures are 0.65 m, 0.30 m and 0.12 m. Through determining the reasonable pillar staggered distance, development of the overburden and surface fractures can be controlled effectively. Finally, the reasonable pillar staggered distance should be greater than 40m in No.1-2 and No.2-2 seams mining in Ningtiaota Coal Mine.
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表 1 浅埋单一煤层开采地表裂缝发育特征实例统计[11-17]
Table 1 Surface fractures development characteristics in shallow single seam mining[11-17]
煤矿 工作面或煤层 采高/ m 埋深/ m 覆岩岩性 地表裂缝发育实测 哈拉沟 22407 5.39 平均136.4 基岩平均88.9 m,松散层42 m 煤柱侧地表裂缝呈弧形,指向工作面内部,不能自修复,动态裂缝能自修复 补连塔 12406 4.81 160.0~220.0 基岩148~200 m,松散层3~30 m 边界裂缝呈“O”形圈分布,主要分布在工作面内部距边界40 m,裂缝带宽46~50 m 51101 5.2 平均146.0 松散层10~30.8 m 地表裂缝呈“O”形分布,边界裂缝呈弧形 陈家山 4-2煤 10.30 约200.0 区内基岩裸露 煤层倾角5°~7°,工作面两侧裂缝边界角70°~86° 大柳塔 12208 7.35 40.4 松散层7 m,基岩33 m 平行于工作面的动态裂缝在沉陷稳定后闭合,而区段煤柱侧边界裂缝不可闭合 22201 3.95 72.5 松散层12 m,基岩61 m 52304 6.96 235.0 松散层30 m,基岩205 m 串草圪旦 4104 3.50 80.7 松散层(红土及黄土)37 m,基岩41 m 动态裂缝超前工作面11 m,间距17.1 m 6106 12.70 105.8 松散层14 m,基岩92 m 动态裂缝超前工作面3.6 m,间距12 m 6104 12.80 117.4 松散层24 m,基岩81 m 动态裂缝超前工作面12 m,间距17.5 m 张家峁 15201 6.30 90.0~220.0 松散层平均50 m,基岩70 m 最外侧煤柱地表裂缝位于巷道外20~25 m 北八特 9煤,井15,井16 40.0~200.0 单一煤层:地表裂缝宽0.1~0.5 m,裂缝长度大于0.5 m,最长100 m 9煤与井15和井16采空区叠置区域,地表塌陷最严重 表 2 浅埋煤层群重复采动地表裂缝发育特征实例统计[18-19]
Table 2 Surface development characteristics in shallow multi-seam repetition mining[18-19]
矿井 工作面 采高/m 埋深/m 层间距/m 覆岩岩性 下煤层开采地表裂缝发育特征实测 柠条塔 1-2煤N1114 1.85 64~156 35.0 基岩厚度54~66 m,土层厚度10~90 m N1114工作面:煤柱侧地裂缝宽度最大0.3 m;N1206工作面:煤柱错距小于10 m时,地表裂缝宽度最大达1.5 m;煤柱错距大于40 m后,地表裂缝宽度0.4 m 2-2煤N1206 5.90 83~205 大柳塔 2-2煤22306 4.50 90 155.6~164.7 地表黄土层厚度约50 m 22306和52304工作面斜交,煤柱叠置区地表裂缝发育严重,地表塌陷槽宽2 m;5-2煤层的煤柱处于2-2煤层采空区下方时,地表裂缝宽度小于0.15 m 5-2煤52304 6.45 250 大柳塔 1-2煤12208 6.00 — 32.6~39.2 地表黄土层厚度约15 m 22201工作面煤柱布置在上煤层采空区下方,裂缝破坏程度比实例2中52304工作面小 2-2煤22201 3.65 75 表 3 柠条塔、大柳塔矿不同煤柱错距地表裂缝宽度
Table 3 Surface fractures width in different pillar staggered distance in Ningtiaota and Daliuta Coal Mine
矿井/煤层 区段煤柱错距/m 煤柱侧地表裂缝宽度/m 柠条塔/1-2与2-2煤 0 1.50 50 0.40 大柳塔/2-2与5-2煤 叠置 2.00 170 0.15 -
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