岩溶含水层饱和-非饱和流动与污染物运移数值模拟  

Numerical simulation of saturated-unsaturated groundwater flow and contaminant transport in a karst aquifer

作　　者：郑小康 杨志兵 Zheng Xiaokang;Yang Zhibing(State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,China;Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,武汉430072 [2]武汉大学水工岩石力学教育部重点实验室,武汉430072

出　　处：《地质科技通报》2022年第5期357-366,共10页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(42077177;41877203)。

摘　　要：岩溶含水层中的地下水是重要的可饮用水来源,由于其复杂的水文地质特征,采用数值模型分析和评价含水层中地下水环境极具挑战性。采用变饱和度流动方程描述含水层基质中的饱和-非饱和流动,采用管道流方程描述岩溶管道中的层流及紊流流动,基于流动解采用对流弥散方程分别描述基质与管道中的溶质迁移过程。根据相关实验数据以及MODFLOW-CFP程序的模拟结果对流动模拟的准确性进行验证,并基于此开展了岩溶管道以及非饱和参数对地下水流动及污染物迁移影响的模拟。结果显示,数值模型能很好地重现含水层中饱和区与非饱和区以及岩溶管道的地下水动态,岩溶管道对含水层的渗流场产生了较大的影响。管道中快速流动的特性使得周围的水向其中汇集,影响了局部流动场,进而使得泄露的污染物质随水流进入管道,快速向管道出口处(泉点)迁移,突破曲线显示管道出口处的污染物浓度响应速度远快于基质中对应的位置,非饱和参数对管道中污染物浓度的响应速率有着不同程度的影响。建立的模型完善了岩溶含水层中非饱和区地下水流动、污染物运移以及基质-管道流动与溶质运移耦合模拟等方面的工作,加深了对岩溶含水层地下水动力学以及污染物迁移过程的认识,对岩溶水文地质及地下水环境等方面具有重要意义。Groundwater in karst aquifers is an important source of drinking water.Due to the complexity of hydrogeological characteristics,it is extremely challenging to analyze and evaluate the groundwater environment in karst aquifers by numerical modeling.In this study,a variable saturation flow equation is used to describe the saturated-unsaturated flow in the aquifer matrix,a pipe flow equation is used to describe the laminar and turbulent flow in karst conduits,and the convective dispersion equation is used to describe solute transport in the matrix and conduits.The accuracy of saturated-unsaturated flow simulation is verified by comparison with experimental data and simulation results from the MODFLOW-CFP code.The numerical model is used to explore the effects of karst conduits and unsaturated parameters on groundwater flow and contaminant transport.These results show that the numerical model can well reproduce the groundwater dynamics in saturated-unsaturated regions and in the karst conduit of the aquifer;furthermore,the karst conduit has a great influence on the seepage field of the aquifer.Relatively rapid flow in the conduit leads to the inflow of surrounding groundwater,affecting the local flow field.As a result,the contaminant is transported through advection in the conduit and is quickly discharged through the outlet(spring).Breakthrough curves show that the response of concentration at the spring is faster than the corresponding location in the matrix.Unsaturated parameters have different effects on the breakthrough characteristics.The model established in this paper improves the simulation methods of groundwater flow,pollutant transport and coupling of matrix-conduit flow with solute transport in the saturated-unsaturated region in karst aquifers.The work deepens the understanding of groundwater dynamics and contaminanttransport in karst aquifers and is thus of great significance to karst hydrogeology and groundwater environment protection.

关 键 词：岩溶含水层 地下水环境 变饱和度 地下水流动 污染物运移 

分 类 号：P641.134[天文地球—地质矿产勘探]