近二十年來，垂直循環井已被證實為有效的含水層污染整技術，除應用於含水層整治工作外，垂直循環井也用來進行含水層水力試驗，推估水文地質參數。本研究發展異向垂直循環流場溶質傳輸數學模式，能夠描述及預測在異向性含水層中，垂直循環井流場之溶質傳輸。數學模式發展首先求解垂直循環井周圍的穩態洩降之解析解，利用洩降解析解可計算孔隙流速於徑向水平與垂直方向之分量；計算所得流速則代入二維圓柱座標移流-延散傳輸方程式描述垂直循環井周圍之溶質傳輸，再藉由Laplace轉換有限差分法求解二維圓柱座標移流-延散傳輸方程式，可得到含水層內溶質濃度分布。所得模式將用以分析抽/注水井篩長度與位置、水力傳導係數異向比、縱向延散度、延散度異向比、抽/注水流率與注入方式對溶質傳輸之影響，分析結果顯示，注水井篩段長度變長及抽水井篩段往下移，能夠使溶質傳輸垂直距離增加，而水平分布範圍會稍微減少，但若注水井篩段與抽水井篩段間距離太大此效應則不明顯；另外水力傳導係數異向比愈大，溶質於含水層中傳輸的水平分布範圍也愈大；縱向延散度增加則是會使傳輸的水平範圍增加，而溶質濃度分布也較為平均；延散度異向比對於溶質傳輸的範圍幾乎沒有影響；抽/注水流率增加會使溶質傳輸速度增加，傳輸的影響範圍也會有些微增加，此外，若採用連續注入方式注入溶質，對於溶質傳輸的範圍不但不會增加，反而會下降；研究所發展之模式能模擬溶質藉由垂直循環井進入含水層後的傳輸範圍，並且也能夠做為含水層整治工作參考。 Vertical circulation well (VCW) technique is a promising innovative technology for cleanup of the contaminated aquifer. Besides being used for injecting remedial compound to enhance aquifer remediation, vertical circulation well has also been applied to determine aquifer hydraulic or transport parameters based on analyzing the drawdown or the breakthrough curves in the extraction and injection interval. This study developed a mathematical model for describing solute transport in the anisotropic flow field. In developing the mathematical model, a steady-state analytical solution for drawdown distribution around a vertical circulation well will be obtained and used to yield the horizontal and vertical components of the pore water velocity. The two-dimensional advection-dispersion equation in cylindrical coordinates will be used for describing solute transport in the anisotropic flow field. The Laplace transform finite difference technique is applied to solve the two-dimensional advection-dispersion equation in cylindrical coordinates. The developed numerical model can be used to simulate the effect of the screen length and location, hydraulic conductivity anisotropy ratio, longitudinal dispersivity, dispersivity anisotropy ratio, injection/extraction rate and injection forms on solute transport. The screen length and location, a hydraulic conductivity anisotropy ratio, longitudinal dispersivity and injection/extraction rate have significant effect on the transport of the solute. The effect of the dispersivity anisotropy ratio and injection forms is negligible. The proposed mathematical model provides a tool for describing the transport regime of the solute, and can be useful in groundwater contamination treatment systems.
