The vertical cut-off wall is a practical means of site contamination control. It is of great importance to predict the service time of a vertical cut-off wall. Previous analytical models on simulation of a cut-off wall neglected the existence of the aquifer, which can lead to simulation errors. An analytical model was developed for contaminant transport in a vertical cut-off wall and an aquifer system. Three cases were considered – that is, advection and diffusion of contaminant towards the same direction, advection and diffusion towards the opposite direction and the pure diffusion case. The analytical solution is obtained by using Laplace transform and binomial theorem. Increasing the scale of the aquifer can extend the breakthrough time. With a fixed hydraulic gradient of 0·5, as the dispersivity of the aquifer increases from 1 to 10 m, the breakthrough time for chloride (Cl⁻) increased by a factor of 1·7. The breakthrough behaviour of chloride is more sensitive to the scale of the aquifer than the breakthrough behaviour of lead is. The breakthrough time of lead obtained by the single-layer model is always longer than that of the proposed model due to overestimation of retardation.

中文翻译：

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防渗墙和含水层系统中污染物迁移的分析模型

垂直的防渗墙是现场污染控制的实用手段。预测垂直防渗墙的使用时间非常重要。以前的模拟防渗墙分析模型忽略了含水层的存在，这可能导致模拟错误。建立了一个分析模型，用于污染物在垂直防渗墙和含水层系统中的传输。考虑了三种情况–即污染物向同一方向的对流和扩散，向相反方向的对流和扩散以及纯扩散情况。通过使用拉普拉斯变换和二项式定理获得解析解。增加含水层的规模可以延长突破时间。在固定水力梯度为0·5的情况下，随着含水层的分散性从1增加到10 m，⁻）增加了1·7倍。与铅的穿透行为相比，氯化物的穿透行为对含水层的规模更敏感。由于高估了延迟，单层模型获得的铅穿透时间总是比所提出的模型更长。