ISSN 1000-3665 CN 11-2202/P

    湘中煤炭坝矿区地下水位变化诱发的岩溶塌陷机理及易发性评价

    Mechanism and susceptibility evaluation of karst collapse induced by groundwater level fluctuation in Meitanba mining area, Central Hunan

    • 摘要: 矿区开采活动与岩溶发育条件叠加,极易诱发岩溶塌陷,这一现象在矿坑排水和闭坑水位恢复过程中表现尤为突出。传统监测方法受监测点数量限制,难以全面把握区域地下水动态特征,导致岩溶塌陷精准预警与易发性评价精度受限。以湘中煤炭坝典型岩溶发育矿区为研究对象,综合地质调查、钻孔勘探及历史水位监测数据,利用GMS软件构建了地下水数值模型模拟地下水位变化,探究在矿坑排水与闭坑水位恢复过程中水位变化诱发岩溶塌陷的机理,并用历史水位监测数据进行验证,揭示了地下水位波动与历史塌陷事件的响应关系;选取岩溶发育程度、覆盖层厚度、地下水位变化速率及历史塌陷点分布等指标,采用层次分析法与模糊综合评价法开展了岩溶塌陷易发性分区评价。结果表明,所构建的地下水数值模型精度良好,72%区域的水位预测误差小于0.5 m;岩溶塌陷是地下水位变化引发上覆盖层土层软化、潜蚀、气压力效应以及浮力改变等多因素共同作用的结果;湘中煤炭坝地区当地下水水位上升时变化速率接近或超过0.51 m/h时和水位下降时变化速率接近或超过0.96 m/h时,极易引发岩溶塌陷;鉴于地下水位波动频繁且受多重因素影响,从风险预警防范角度,采用就低原则,将水位变化速率接近或超过0.51 m/h作为研究区诱发岩溶塌陷的地下水水位变化阈值;基于该关键阈值与多源数据融合的易发性评价模型,预测精确率可达91.4%。研究成果可为矿区岩溶塌陷风险防控及同类地区地质灾害防治提供科学依据与技术参考。

       

      Abstract: Mining activities superimposed on karst terrains are highly susceptible to triggering karst collapse, particularly during mine dewatering and post-closure groundwater recovery. Traditional monitoring methods often fail to adequately capture regional groundwater dynamics due to sparse monitoring networks, thereby limiting the accuracy of karst collapse early warning and susceptibility assessments. Here, this study investigated the Meitanba Mining Area in central Hunan, a region characterized by extensive karst development, integrating geological survey, borehole exploration and historical water level monitoring, and established a groundwater numerical simulation model via GMS software to simulate variations in groundwater levels. The mechanism of karst collapse geological hazards induced by water level fluctuations during the process of mine drainage and pit water level recovery processes was explored. Historical water level monitoring was used to verify the model. Furthermore, the response relationship between groundwater level fluctuations and historical collapse events was revealed. Combining evaluation indicators such as karst development degree, overburden thickness, groundwater level variation amplitude, and historical collapse distribution, susceptibility zoning assessment was conducted using the Analytic Hierarchy Process (AHP) and Fuzzy Comprehensive Evaluation Method. The numerical simulations demonstrated good predictive performance, with groundwater-level prediction errors of less than 0.5 m across 72% of the study area. The synergistic effects of factors such as overburden soil softening, suffosion, air pressure fluctuations, and buoyancy changes induced by groundwater level variations contribute to karst collapse hazards. In the Meitanba area of central Hunan, karst collapse is highly likely to occur when the variation amplitude of groundwater level approaches or exceeds 0.51 m/h during water level rise, or approaches or exceeds 0.96 m/h during water level decline. Given that groundwater level fluctuates frequently and is affected by multiple factors, the lower-limit principle is adopted for risk early warning and prevention. Accordingly, the groundwater level variation amplitude of approaching or exceeding 0.51 m/h is defined as the threshold for inducing karst collapse in the study area. The susceptibility evaluation model integrating this critical threshold with multi-source data achieves an accuracy of 91.4%, providing valuable insights for karst collapse risk prevention in mining areas and disaster mitigation practices in similar regions.

       

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