Numerical models for mixing corrosion in natural and artificial karst environments
Numerical models for mixing corrosion in natural and artificial karst environments
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DOI：
10.1029/2002wr001707
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发表时间：
2003-04
影响因子：
5.4
通讯作者：
G. Kaufmann
中科院分区：
文献类型：
--
作者：
G. Kaufmann
本文研究了岩溶含水层中初始小裂隙的化学溶解扩大问题。含水层中的水流是由汇点和水面之间的水头差驱动的，水流取决于含水层中小裂隙和裂缝的渗透性。裂缝的封闭受补给的化学成分控制，因为相对于方解石不饱和的水能够溶解裂缝壁的物质。随着时间的推移，裂缝扩大，含水层内的渗透性显着增加，流动变得非常不均匀。两个不同的过程被认为是：由于正常的腐蚀，其中水是不饱和的方解石，和由于混合腐蚀，其中两个解决方案饱和的方解石，但具有不同的二氧化碳浓度混合和所得的解决方案再次成为不饱和的放大。混合腐蚀的重要性进行了讨论两个边界条件：一个天然的岩溶含水层模拟与固定补给边界条件代表下沉流，和一个人工岩溶含水层模拟与固定的头边界条件代表一个水库。在这两种情况下，混合腐蚀是重要的，特别是如果补给的特点是几乎饱和的化学。混合腐蚀显著改变了不断变化的通道模式，因为溶液混合引起的溶解可能发生在含水层深处。混合腐蚀也减少了含水层的突破时间，并可能导致大坝下方的严重渗漏，即使蓄水几乎饱和的方解石。
The enlargement of initially small fractures in a karst aquifer by chemical dissolution is studied. Flow in the aquifer is driven by head differences between sinks and resurgences, and flow depends on the permeability of small fissures and fractures in the aquifer. Enlargement of fractures is controlled by the chemical composition of the recharge, as water undersaturated with respect to calcite is able to dissolve material from the fracture walls. As fractures are enlarged with time, permeability within the aquifer increases significantly, and flow becomes very heterogeneous. Two different processes are considered: enlargement due to normal corrosion, where water is undersaturated with respect to calcite, and enlargement due to mixing corrosion, where two solutions saturated with respect to calcite but with different carbon dioxide concentrations mix and the resulting solution becomes undersaturated again. The importance of mixing corrosion is discussed for two boundary conditions: A natural karst aquifer is modeled with fixed recharge boundary conditions representing sinking streams, and an artificial karst aquifer is simulated with fixed head boundary conditions representing a reservoir. In both cases, mixing corrosion is important, especially if recharge is characterized by an almost saturated chemistry. Mixing corrosion significantly changes the evolving passage pattern, as dissolution due to mixing of solutions is possible deep in the aquifer. Mixing corrosion also reduces breakthrough times of the aquifer and can result in dramatic leakage underneath dam sites, even if the impounded water is almost saturated with respect to calcite.