Abstract We develop a new analytical infiltration model to determine water flow dynamics around layer interfaces during infiltration process in layered soils. The model mainly involves the analytical solutions to quadratic equations to determine the flux rates around the interfaces. Active water content profile behind the wetting front is developed based on the solution of steady state flow to dynamically update active parameters in sharp wetting front infiltration equations and to predict unsaturated flow in coarse layers before the front reaches an impeding fine layer. The effect of water backfill to saturate the coarse layers after the wetting front encounters the impeding fine layer is analytically expressed based on the active water content profiles. Comparison to the numerical solutions of the Richards equation shows that the new model can well capture water dynamics in relation to the arrangement of soil layers. The steady state active water content profile can be used to predict the saturation state of all layers when the wetting front first passes through these layers during the unsteady infiltration process. Water backfill effect may occur when the unsaturated wetting front encounters a fine layer underlying a coarse layer. Sensitivity analysis shows that saturated hydraulic conductivity is the parameter dictating the occurrence of unsaturated flow and water backfill and can be used to represent the coarseness of soil layers. Water backfill effect occurs in coarse layers between upper and lower fine layers when the lower layer is not significantly coarser than the upper layer.

中文翻译：

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层状土壤入渗过程中非饱和流和回填水的预测

摘要 我们开发了一种新的分析渗透模型，以确定层状土壤中渗透过程中层界面周围的水流动力学。该模型主要涉及二次方程的解析解，以确定界面周围的通量率。润湿锋后方的活性含水量剖面是基于稳态流动的解而开发的，以动态更新尖锐润湿锋入渗方程中的活动参数，并在锋面到达阻碍细层之前预测粗层中的非饱和流动。在润湿前沿遇到阻碍细层后，回填水使粗层饱和的效果基于活性含水量分布进行分析表达。与理查兹方程的数值解的比较表明，新模型可以很好地捕捉与土层排列相关的水动力学。当润湿前沿在非稳态渗透过程中首先通过这些层时，稳态活性含水量剖面可用于预测所有层的饱和状态。当不饱和润湿前沿遇到粗层下面的细层时，可能会发生回填水效应。敏感性分析表明，饱和导水率是决定不饱和流和回填水发生的参数，可以用来表示土层的粗度。当下层不明显比上层粗时，水回填效应发生在上层和下层细层之间的粗层中。