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摘要:
矿井涌水对井下安全生产存在潜在威胁,同时可能引发因矿区地下水位下降造成的地表植被难以逆转的演替退化。针对涌水量数值模型构建时边界条件概化不准确和水文地质参数选用不可靠等关键问题,以准确预测矿井涌水量保障煤层安全开采为目标,并为研究区沙漠植被的保护提供理论和数据支撑,选择以天然边界作为研究区周界,在充分收集与分析钻探、物探、抽水试验、地下水长观和矿井采空区范围及其涌水量等资料的基础上反复修正模型,构建了较为逼真的地下水三维非稳定流数值模型。此外依据矿井采空区拓展进程及其涌水量和地下水监测数据等进行模型模拟识别,论证了该模型的合理性和可靠性。利用所建立的数值模型预测了煤层开采条件下的矿井涌水量和潜水位降深场,进而基于潜水位埋深与沙漠植被关系分析了潜水位下降对沙漠植被的影响。结果表明:根据矿区先期煤层开采预测矿井涌水量为 3.08×104 m3/d,引起矿区内潜水位下降2.08~2.35 m,将导致矿区内代表性植被沙柳和小叶杨的长势变差、甚至部分枯萎,呈现由中生植被类型向旱生植被方向的演替趋势。研究结果为研究区提供了较准确的涌水量预测值,可以为制定科学有效的矿区沙漠植被保护措施以及为类似地下水流数值模型的构建提供可靠的思路。
Abstract:Mine inflow threats mine safety production underground, and may trigger a decline in the groundwater level in the mine area, causing irreversible successional degradation of surface vegetation. In view of the key problems such as inaccurate generalization of boundary conditions and unreliable selection of hydrogeological parameters when constructing numerical models of water inflow, this study aims to accurately predict mine water inflow, ensure the safe mining of coal seams, and provide theoretical and data support for the protection of desert vegetation in the study area. The natural boundary is selected as the perimeter of the research area, and the model is repeatedly revised on the basis of fully collecting and analyzing the data of drilling, geophysical prospecting, pumping test, groundwater long-term monitering, and the scope of the mine goaf and its water inflow, and thus a more realistic three-dimensional unstable flow numerical model of groundwater is constructed. In addition, the model simulation and identification are carried out according to the expansion process of the mine goaf and its water inflow and groundwater monitoring data, which demonstrates the rationality and reliability of the model. The established numerical model is used to predict the mine inflow and submersible level depth drop under coal seam mining conditions, and then the influence of diving level decline on desert vegetation is analyzed based on the relationship between diving depth and desert vegetation. The results show that the predicted water inflow in the mine is 3.08×104 m3/d, resulting in a decrease of 2.08−2.35 m in the diving level in the mine area, which will lead to the deterioration or even partial withering of the representative vegetation sand willow and poplar in the mine area, showing a succession trend from mesophytic vegetation type to xerophytic vegetation. The results can provide more accurate water inflow prediction in the study area, scientific and effective measures for the protection of desert vegetation in mining areas, and reliable treatment ideas for the construction of similar numerical models of groundwater flow.
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Key words:
- mine inflow /
- numerical simulation /
- desert vegetation /
- phreatic water level /
- natural border
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表 1 模型区水文地质参数分区与参数值成果表
Table 1. Hydrogeological parameter division and values in the model area
分层 分区号 地层 渗透系数 /(m·d−1) 给水度 弹性释水率/m−1 备注 水平 垂直 第1层 Ⅰ 第四系砂土层 4.5 4.5 0.17 — 二道河则沟域 Ⅱ 第四系砂土层 3.7 3.7 0.15 — 头道河则沟域 第2层 全区 更新统黄土层 6.5×10−2 8.5×10−2 — 1×10−6 第3层 全区 侏罗系岩层 3.6×10−2 9.0×10−5 — 1×10−5 导水裂隙带之上原岩层 第4层 Ⅰ 侏罗系岩层 20.0 85.0 — 1×10−5 导水冒裂带 Ⅱ 侏罗系岩层 3.6×10−2 9.0×10−5 — 1×10−5 冒裂带的两侧原岩层 第5层 Ⅰ 侏罗系煤层 — — — 1×10−5 采空区 Ⅱ 侏罗系煤层 3.6×10−2 9.0×10−5 — 1×10−5 采空区的两侧原煤层 表 2 研究区的地下水补排量预测结果表
Table 2. Groundwater recharge and discharge prediction results in the study area
补排项 补排量/(104 m3·d−1) 现状 预测
期末差值(预测
期末–现状)补给项 降水入渗 16.38 16.38 0 二类边界 1.11 1.11 0 合计 17.49 17.49 0 排泄项 潜水蒸发 6.18 5.76 −0.42 潜水溢出 8.64 8.57 −0.07 一、二类边界 0.42 0.42 0 矿坑涌水 2.41 3.08 0.67 合计 17.65 17.83 0.18 均衡差 −0.16 −0.34 −0.18 表 3 研究区植物长势与潜水位埋深关系表
Table 3. Relationship between plant growth and depth to the water table in the study area
植物
名称潜水位
埋深/m生长
情况植物
名称潜水位
埋深/m生长
情况沙柳 0.5~1.5 生长旺盛 小叶杨 0.5~1.5 生长旺盛 >1.5~3.0 生长良好 >1.5~3.0 生长良好 >3.0~5.0 生长正常 >3.0~5.0 生长正常 >5.0~8.0 生长较差 >5.0~8.0 生长较差,
其中部分枯萎>8.0 生长差 >8.0 生长差,
其中大都枯死沙嵩 0.5~1.5 生长旺盛 旱柳 0.5~3.0 生长旺盛 >1.5~3.0 生长良好 >3.0~5.0 生长良好 >3.0~7.0 生长正常 >5.0~8.0 生长正常 >7.0~12.0 生长较差 >8.0~12.0 生长较差,
其中部分枯萎>12.0 生长差 >12.0 生长差,
其中大都枯死表 4 研究区现状植物生长情况分布面积
Table 4. The distribution area of current plant growth in the study area
植物 生长状态 分布面积 /km2 模型区(含矿区) 矿区内 沙柳、小叶杨 正常生长 399.25 69.64 生长较差、部分枯萎 198.85 20.72 沙嵩、旱柳 正常生长 507.74 90.36 表 5 研究区预测期末植物生长情况分布面积表
Table 5. Distribution area of plant growth in the study area at the end of the prediction period
植物 生长状态 分布面积 /km2 模型区(含井田) 井田内 沙柳、小叶杨 正常生长 373.64 50.83 生长较差、部分枯萎 224.46 39.53 沙嵩、旱柳 正常生长 597.88 90.14 生长较差、部分枯萎 0.22 0.22 -
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