西部浅埋煤层开采顶板含水层水量损失动力学过程特征

Dynamics process analysis of groundwater quantity loss of roof aquifer with shallow seam mining in Western China

受保护含水层水量损失的定量计算是"保水采煤"理论发展目前面临的瓶颈问题。利用覆岩破坏数值模拟方法,将陕北榆神矿区典型覆岩结构下煤层开采顶板水量损失过程划分成单一风化基岩失水和萨拉乌苏组、风化基岩复合失水模式;基于系统动力学理论,构建了2种水量损失模式动力系统模型,建立了实际疏放与无疏放状态水量损失过程之间的数学关系,求解了水量损失动力系统模型参数,确定了水量损失峰值及发生位置、水量损失动态平衡值及发生位置;通过开采扰动区水流数值模拟,计算了2种模式单位走向长度水量损失强度。结果表明:覆岩组合特征控制着煤层采动含水层动、静储量叠加释放过程,决定了工作面采动顶板水量损失模式; 2种水量损失模式相比,复合模式下水量损失峰值和动态平衡值均较大;钻孔疏放水显著削减了推采过程水量损失峰值强度,改变了水量损失方式和时机,但采动过程水量损失动态平衡值及顶板水资源损失总量并未发生变化;两种模式下工作面采动,水资源损失总量以及水资源损失强度中松散层和风化基岩水占比计算结果,揭示了古近系黏土隔水层对于萨拉乌苏组潜水保护的重要意义。研究结果为"保水采煤"理论在工作面尺度含水层水量损失及保护的定量计算提供了新思路。

Coal seam mining destroys aquifers,resulting in a large loss of water resources,and it is of great significance to implement water conservation during mining.Quantitative calculation of water loss in protected aquifer is the bottleneck of water-conserving mining theory at present.Based on the results of numerical simulation of overburden failure in yushen mining area of northern Shaanxi Province,the process of roof water loss with mining is divided into two modes,one is the single weathered bedrock water-filling model,the other is composite water-filling model of Sarawusu Formation and weathered bedrock.Based on the system dynamics theory,we proposed the double-exponential decay model to describe the water loss modes,established the mathematical relationship of water loss process with actual drainage and without drainage,and calculate the approximate solution of model parameters with physical meaning determined by McLaughlin formula,as well as the water loss process with peak value and equilibrium value,and their occurring location.In addition,we simulated the flow process in mining disturbance area by Comsol Multiphysics,calculated the intensity of water loss per unit strike distance.The results indicated that,overburden combination characteristics control the multiple release process of dynamic and static reserves of roof aquifer in mining,and determine the water loss mode,when compared with the two water loss modes,the peak value and dynamic equilibrium value of water loss under the combined mode are larger,drilling water drainage significantly reduces the peak intensity of water loss during mining,changes the mode and timing of water loss of roof aquifer,but cannot change the dynamic equilibrium value of water loss and the total amount of water loss during mining,the calculation results of total water resources loss and proportion of loose layer and weathered bedrock water in water resources loss intensity,indicate the protective effect of Paleogene clay aquifer on phreatic water storaged in Salawusu Formation.The conclusion provides a new way for the quantitative calculation of water loss and protection of aquifer at working face scale.