东部草原区露天煤矿开采对地下水系统影响与帷幕保护分析

Analysis of influence of open-pit coal mining on groundwater system and curtain wall protection in grassland area of Northeastern China

我国东部呼伦贝尔草原地区是以露天开采为主的重要煤电基地,但是针对草原区露天煤矿开采对地下水系统影响及其水资源保护等问题研究较为不足。以呼伦贝尔草原宝日希勒露天矿区为研究对象,根据矿区煤炭资源开发与疏排水特征,将矿区露天矿开采历史划分为初期、剧增期与稳定期3个阶段。应用地下水系统数值仿真技术,系统分析了露天矿区疏排水对地下水系统的影响规律。结果显示:第1阶段(初期),由于宝日希勒露天煤矿首采区疏排水影响(疏排水强度2.3×104 m 3/d),矿区范围内平均水位降深小于5 m;第2阶段(剧增期),宝日希勒露天矿西侧的东明露天矿相继开发,由于东明露天井田富水性好的松散含水层(渗透系数大于35 m/d)接受莫日格勒河地表水体补给充分,导致矿区疏排水强度增加至19.47×104 m 3/d,矿区范围内平均水位降深大于10 m;第3阶段(稳定期),宝日希勒露天矿首采区闭坑后2采区相继开采,矿区疏排水量趋于稳定(14.93×104 m 3/d),莫日格勒河地表水体渗漏补给松散层地下水强度约为11.02×104 m 3/d,约占东明露天矿疏排水量的80%,平均水位降深大于15 m。最后,根据矿区水文地质条件、帷幕减渗条件下地下水流场以及露天矿剥离开采条件下含水层涌水特征,构建了受强富水强补给露天矿在帷幕墙减渗条件下地下水系统仿真模型,评价了帷幕墙构建对疏排水的影响程度,模拟得出帷幕墙长度为4 km的条件下,疏排水量减少至6.65×104 m 3/d,降幅约为51.81%,总结提出帷幕墙阻水减渗方案是矿区针对强富水、强补给含水层地下水保护性开采与露天矿减少疏排水量的有效手段。

The Hulunbuir grassland area in Eastern China is an important coal and power base mainly with open-pit mining.In view of the insufficient research on the influence of open-pit coal mining on groundwater resources in Hulunbuir grassland area,the authors toke Baorixile open-pit mining area for this study,and divided the history of open-pit mining into three stages:initial stage,rapid increase stage and stable stage according to the characteristics of coal resources development and drainage intensity.By means of numerical simulation technology,the influence of drainage on the groundwater system in open-pit mining area was analyzed systematically.The simulation results show that in the first stage(initial period),due to the influence of drainage in the first mining area of Baori Sheller open-pit coal mine(drainage intensity was 2.3×104 m 3/d),the average water level drop in the mining area was less than 5 m.In the second stage(rapid increase period),Dongming open-pit mine on the west side of Baori Schiller open-pit mine was exploited successively.As the loose aquifer near the surface of Dongming open-pit mine received sufficient recharge from surface water of Morigler river,the drainage intensity of the mining area increased to 19.47×104 m 3/d,and the average water level in the mining area fallen more than 10 m.In the third stage(stable period),after the closure of the first mining area in Baori Shiller open-pit mine,the No.2 mining area had been exploited successively.However,the drainage intensity of the whole mining area tended to be stable(14.93×104 m 3/d),and the average water level drop in the mining area was more than 15 m.The loose medium aquifer groundwater recharged by river seepage was about 11.02×104 m 3/d,accounts for 80%of the drainage volume in Dongming open pit mine.Finally,according to the hydrogeological conditions of the study area,the characteristics of groundwater flow field under the curtain wall conditions,and the water inflow from aquifer under open pit mining conditions,the simulation model of groundwater system under the condition of curtain wall was constructed.The influence degree of curtain wall on drainage intensity was calculated and evaluated which indicates that the drainage volume decreases to 6.65×104 m 3/d and decrease range is about 51.81%under the condition of 4 km long curtain wall.It can be seen that the curtain wall water-resisting and seepage-reducing technology is an effective mean of groundwater protection for the strong water-rich and strong recharge aquifers in the open-pit mining areas.