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浅埋煤层重复开采扰动条件下矿井水水化学特征演化规律及其意义

Hydrochemical evolution law of mine water under repeated mining disturbance in shallow buried coal seams and its significance

  • 摘要: 蒙陕接壤浅埋煤层区在长期大规模开采后上层煤组多已开采完成,正在进行下层煤组开采,在重复开采扰动后,研究区矿井涌水呈现出水质变化、水量增大的特点。开展蒙陕接壤浅埋煤层区重复扰动条件对下组煤工作面顶板矿井涌水的水化学特征及水量变化的影响的研究,是开展防治水工作与水资源保护的前提。通过收集地表水、第四系松散层地下水、基岩地下水、采空区积水及矿井水水样共计56组,针对水质全分析结果运用数理统计、水化学特征、离子比例系数及氢氧同位素分析等方法,结合河流流量监测值变化情况,定性分析了矿井水水质演化特征,定量评价了充水水源的补给比例。研究结果表明,北翼地下水随着埋深增加水化学类型由HCO3—Ca·Na型转变为HCO3—Na型,南翼矿井水、含水层地下水与地表水水化学类型相似,均为HCO3—Na型,其水化学组分形成主要受水−岩作用控制,还受到反向阳离子交替吸附作用影响,主要离子成分均来源于硅酸盐矿物的溶解;2号煤矿井水的主要补给水源为基岩含水层(66.2%)与第四系含水层(21.5%),南翼3号煤矿井水的主要补给水源为地表水及浅层地下水,其对应补给比例分别为23.6%与29.6%,基岩含水层补给比例下降为46.8%,重复扰动形成的导水裂隙带导通了地表,成为地表水对矿井水补给的主要充水通道。研究给出了适用于浅埋煤层区重复扰动条件下地下水及矿井水的补给路径及强度模型,并提出了“常态化监测−汛期预警−采后改造”一体的针对性水害防治建议,对推动区域水资源保护、保证区域煤矿开采安全具有重要指导意义。后续的研究中应将推采速度、侧向补给强度纳入研究变量,综合研究其对矿井涌水量质变化的影响规律。

     

    Abstract: In the shallow coal seam area at the border of Inner Mongolia and Shaanxi, most of the upper coal groups have been mined out after long-term large-scale mining, and the lower coal groups are currently being mined. Following repeated mining disturbances, the mine water inflow in the study area exhibits characteristics of water quality changes and increased water volume. Investigating the causes of the impacts of repeated disturbance conditions on the hydrochemical characteristics and water volume changes of roof mine water in the working faces of the lower coal group is a prerequisite for conducting water prevention and control work and water resource protection. A total of 56 water samples were collected, including surface water, Quaternary loose layer groundwater, bedrock groundwater, goaf water, and mine water. Based on the complete water quality analysis results, mathematical statistics, hydrochemical characteristics analysis, ion proportional coefficient analysis, and hydrogen-oxygen isotope analysis were applied. Combined with the changes in river flow monitoring values, the evolution characteristics of mine water quality were qualitatively analyzed, and the recharge proportions of water-filling sources were quantitatively evaluated. The results show that the hydrochemical type of groundwater in the northern wing changes from HCO3—Ca·Na type to HCO3—Na type with increasing burial depth. The hydrochemical types of mine water, aquifer groundwater, and surface water in the southern wing are similar, all being HCO3—Na type. The formation of their hydrochemical components is mainly controlled by water-rock interaction and also affected by reverse cation exchange adsorption, with the main ionic components derived from the dissolution of silicate minerals. The main recharge sources of mine water in Coal Mine 2 are the bedrock aquifer (66.2%) and the Quaternary aquifer (21.5%). The main recharge sources of mine water in Coal Mine 3 in the southern wing are surface water and shallow groundwater, with corresponding recharge proportions of 23.6% and 29.6% respectively, while the bedrock aquifer recharge proportion decreases to 46.8%. The water-conducting fractured zone formed by repeated disturbances has connected the surface, becoming the main water-filling channel for surface water recharge to mine water. This study presents a recharge path and intensity model for groundwater and mine water applicable to shallow coal seam areas under repeated disturbance conditions, and proposes targeted water disaster prevention and control suggestions integrating “normalized monitoring - flood season early warning - post-mining reconstruction”. The research has important guiding significance for promoting regional water resource protection and ensuring the safety of regional coal mining. In subsequent research, the advancing speed and lateral recharge intensity should be included as research variables to comprehensively consider their influence laws on the quality and quantity changes of mine water inflow.

     

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