裂隙水溶质运移的裂隙网络结构控制与模拟概化研究

Fractured bedrocks are distributed widely and groundwater in the fractured rocks is more subject to contamination. Since the distribution and structure of groundwater flow paths in fractured rocks are considerably complicated, particularly, for the fracture networks bearing major fractures, in which both laminar flow and turbulent flow may occur in different parts. As a result, it is still necessary to further investigate the mechanism and pattern in controlling of the structures of fracture networks on groundwater solute transport, and to well establish the methods of conceptualizing and simplifying the fracture networks. Firstly, the complex fracture network generated based on the fracture disc model is built and the solute transport experiments are conducted in the lab by integrating with the different experimental conditions including the various solute input patterns corresponding with space and time. Then, the discrete pipe model fracture networks are created and the solute transport experiments are carried out with the same controlling conditions as applied in the solute transport experiments conducted in the discrete disc model fracture networks. The characteristics of solute transport and patterns of solute distribution are investigated by monitoring the water head, solution conductivity and solution concentration in the experiments. Furthermore, a mathematic model coupling solute transport in the complex fracture networks with the corresponding flow filed would be recognized according to the experiment data. Additionally, the current numerical models and computer simulation systems are examined and they may be improved for solute transport in the discrete fracture networks. By combining the limited experimental results and lots of numerical simulation results from various representing scenarios, the primary factors controlling solute transport in the fracture networks can be comprehensively identified. The investigation results are expected to offer the theoretical foundation for effective protection on groundwater in the fractured rocks.

基岩裂隙水分布广泛且易遭受污染，因其赋存与运移空间结构复杂且流态多变，尤其含较大断裂(主断裂)的裂隙网络含水系统，溶质运移受控于网络结构的内在关系及作用机理仍需进一步查明，同时，在实践中裂隙水溶质运移模拟也需简单的裂隙网络概化方法。针对上述亟待解决问题，首先构建复杂的仿真裂隙网络物理模型，设计不同时空分布特征的溶质组分输入方式，开展典型裂隙网络结构的溶质运移室内实验研究，进一步研究构建简单而近似等效的溶质运移裂隙网络管道流物理模型。通过选取并监测模拟装置中不同时空点的水头和溶质浓度变化，研究溶质在主断裂和周围裂隙网络中的时空分布特征及运移规律，建立溶质运移与流场的耦合关系，经本实验进一步验证与修正现有的裂隙网络溶质运移数值模型，通过物理与数值模拟综合研究含主断裂的裂隙网络结构对溶质迁移过程的控制作用，识别主控因子，提出裂隙水溶质运移模拟的概化方法，为基岩裂隙水污染有效防控提供重要依据。

基岩裂隙水分布广泛且易遭受污染，因其赋存与运移空间结构复杂且流态多变，尤其针对隙宽等几何参数不一的裂隙组成的裂隙网络含水系统，溶质运移受控于网络结构与裂隙几何现状的内在关系及作用机理仍需进一步查明；同时，在实践中裂隙水溶质运移模拟也需简单的裂隙网络概化方法。针对上述亟待解决问题，首先构建了简单的圆盘裂隙物理模型与复杂的仿真裂隙网络物理模型，设计不同边界条件及典型时空分布特征的溶质组分输入方式，开展了典型裂隙网络结构的溶质运移室内实验研究；通过选取并监测模拟装置中不同时空点的水头和溶质浓度变化，研究并获得了裂隙及裂隙网络中流体渗流与溶质运移的时空分布特征及规律，建了立溶质运移与流场的耦合关系；进一步研究了简单而可近似等效于圆盘裂隙的溶质运移裂隙管道流模型，提出了裂隙网络管道流模型概化方法。通过大量的裂隙渗流与溶质运移物理模型模拟实验，并应用地下水渗流与溶质运移模拟软件，综合分析裂隙网络结构与边界条件对溶质迁移过程的控制作用，识别出主控因子，为基岩裂隙水污染风险评价与污染有效防控提供重要理论依据与方法支撑。