Reasonable coal pillar setting and roadway surrounding rock control technology in close-distance coal seam working face
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摘要: 為探究近距離煤層工作面煤柱合理留設寬度以及回采巷道圍巖控制技術,以回坡底煤礦近距離煤層開采為工程背景,通過數值模擬、理論分析、現場實踐等技術手段對不同寬度條件下煤柱破壞演化過程、影響因素、底板破壞范圍以及11號煤層回采巷道圍巖控制技術進行了深入研究。研究結果表明:(1)煤柱在預留煤柱時期、區段煤柱時期、保護煤柱時期、孤島煤柱時期四個階段過程中,煤柱破壞范圍逐漸增大;煤柱彈性核占比均隨煤柱寬度的增加而增加,本煤層回采巷道隨煤柱寬度的增加從非對稱性破壞逐漸演化為對稱性破壞。煤柱破壞寬度與煤層傾角、黏聚力、煤柱寬度、內摩擦角和泊松比等因素成反比關系,只與埋深成正比關系。(2)隨著煤柱寬度增大,煤柱底板破壞寬度與深度會發生變化,且底板破壞集中在煤柱邊緣側,煤柱正下方底板破壞區域較小。(3)煤柱應力集中作用致底板下方最大主應力發生偏轉,底板任意一點與煤柱中心線的距離越大,最大主應力偏轉角度越小;隨著11號煤層巷道與煤柱邊緣距離的增大,巷道圍巖塑性區由傾斜的“X”形分布轉變為傾斜的“8”形分布,再轉化為傾斜的“O”形分布,最終轉化為橢圓形分布;離煤柱距離較近時,巷道往往出現非對稱性破壞,支護也要采取非對稱支護形式。Abstract: To explore the reasonable width of the coal pillar and surrounding rock control technology of the mining roadway in a close-distance coal seam working face, this paper took the mining of No.10 and No.11 coal seams of the Huipodi coal mine as the engineering background. Through numerical simulation, theoretical analysis, field practice, and other technical means, the evolution of the coal pillar failure, influencing factors, and damage range of floor under different widths were analyzed. The surrounding rock control technology of the mining roadway was studied in depth. Results show that: (1) During the four stages of reserved, section, protective, and isolated coal pillars, the damage scope of the coal pillar gradually increased. The proportion of the elastic core of the coal pillar increased with the increase of the coal pillar width. The mining roadway in this coal seam evolves from asymmetric failure to symmetrical failure. The failure width of the coal pillar is directly proportional to the buried depth and inversely proportional to the coal seam dip angle, cohesion, coal pillar width, internal friction angle, and Poisson’s ratio. (2) With the increase in coal pillar width, the width and depth of the coal pillar floor failure will change. Moreover, the floor failure concentrated on the side of the coal pillar edge, and the damaged floor area under the coal pillar is observed to be small. (3) The maximum principal stress under the floor deflects owing to the concentrated stress of the coal pillar. The larger is the distance between any point of the floor and the centerline of the coal pillar, the smaller is the deflection angle of the maximum principal stress. With the increase in the distance between the roadway and coal pillar edge, the plastic zone of the roadway surrounding rock initially changes from an inclined X-shaped distribution to an inclined 8-shaped distribution, which then changes to an inclined O-shaped distribution and finally to an elliptical distribution. When the distance from the coal pillar is close, the roadway often shows an asymmetric failure, and the support should also take the form of asymmetric support.
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圖 1 巷道開挖、工作面回采與煤柱演化過程. (a)預留煤柱時期; (b)區段煤柱時期; (c)保護煤柱時期; (d)孤島煤柱時期
Figure 1. Roadway excavation, working face mining, and coal pillar evolution process: (a) period of the reserved coal pillar; (b) period of the section coal pillar; (c) period of the protection coal pillar; (d) period of the isolated coal pillar
圖 12 距煤柱邊緣不同距離下巷道圍巖塑性區分布形態. (a)4 m; (b)6 m; (c)8 m; (d)10 m; (e)12 m; (f)14 m; (g)16 m; (h)18 m; (i)30 m
Figure 12. Plastic zone distribution of the roadway surrounding rock in different distances from the coal pillar edge: (a) 4 m; (b) 6 m; (c) 8 m; (d) 10 m; (e) 12 m; (f) 14 m; (g) 16 m; (h) 18 m; (i) 30 m
圖 13 11-1021巷圍巖破壞情況. (a)靠近煤柱側巷幫; (b)巷道頂板; (c)遠離煤柱側巷幫; (d)靠近煤柱側頂板; (e)遠離煤柱側頂板; (f)靠近煤柱側底板鉆孔; (g)遠離煤柱側底板鉆孔
Figure 13. Surrounding rock failure of 11-1021 roadway: (a) roadway side near the coal pillar; (b) roadway roof; (c) roadway side far away from coal pillar; (d) roof near the coal pillar side; (e) roof far away from the coal pillar; (f) floor drilling hole near the coal pillar side; (g) floor drilling hole away from pillar side
表 1 巖層物理力學參數
Table 1. Rock’s physical and mechanical parameters
Rock stratum Thickness /m Density/
(kg·m?3)Bulk/
GPaShear/
GPaCohesion/
MPaCohesion /MPa Angle of internal friction /(°) Overlying strata 46 2460 10.83 8.13 7.8 5.4 38 Siltstone 8 2680 5.6 4.2 5.2 1.4 29 K2 limestone 8.9 2800 5.57 4.53 5.4 3.8 27 No.9 coal 1 1400 2.08 0.54 1.2 0.64 20 Mudstone 2.3 2600 2.91 1.5 2 2.1 32 No.10 coal 2.65 1420 2.50 1.72 2 1 21 Siltstone 2.82 2680 5.6 4.2 5.1 1.4 29 Mudstone 3.8 2461 6.08 3.47 3 0.6 28 No.11 coal 3.2 1423 2.50 1.72 2.4 1.2 29 Aluminous mudstone 0.8 2100 2.6 1.8 2.65 2 25 Mudstone 3 2461 6.08 3.47 3 0.6 28 Siltstone 2.53 2680 5.6 4.2 5.1 1.4 29 Aluminous mudstone 3 2981 2.17 1 2.4 0.9 25 Quartz sandstone 2 2650 3.05 1.92 4.3 1.6 27 Siltstone 10 2680 5.57 4.2 5.1 1.4 29 Overlying strata 35 2680 5.6 4.18 5.2 1.5 30 -
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