入滲是水分自地表進入到土壤的過程，其重要性包括灌溉策略的制訂發展、 估計地下水補注的時間與數量，以及化學物質在土壤中的傳輸過程。在水文研究 的應用上，有很多估計入滲量的方法曾被提出，例如Green-Ampt model (GAM) (Green and Ampt, 1911)、Richards方程(Richards, 1931)等。在傳統達西尺度中，毛 細壓力常常被假設為定值，稱為平衡毛細壓力，但相關研究顯示，流速較快時， 實際毛細壓力與平衡毛細壓力不相等。此非平衡的毛細壓力稱為動態毛細壓力。 本研究以沙柱實驗，觀測不同暫水深條件下，入滲過程中溼潤面的移動速度。並 搭配GAM與修正型GAM的模式比較，探討在不同材質與粒徑中，流速的變化與 動態毛細壓力的關係，沙粒特性對動態毛細壓力以及入滲現象的影響。;Infiltration happens when water on the ground surface enters the soil. Understanding the infiltration process is important to draw up the irrigating strategies, estimate the time and quantity of the groundwater recharge, and understand the transport of the chemicals in the soil. Mathematical models had been presented to simulate the infiltration process, such as Green-Ampt Model (GAM) (Green and Ampt, 1911) and Richards’ equation (Richards, 1931). In the traditional Darcy-scale model, the capillary pressure is usually assumed as a constant, that is equilibrium capillary pressure. However, studies show that the difference between the capillary pressure and the equilibrium capillary pressure is significant in high flow velocity. This non-equilibrium capillary pressure is called dynamic capillary pressure. In this study, we performed a series of infiltration experiments in sand columns with different types of sands and under different boundary conditions. To show the effects of dynamic capillary pressure, we compared the results of the experiments with the simulations from the GAM and the modified GAM which takes the dynamic capillary pressure into account. We found that the dynamic effects are more significant during the infiltrations in sands with large grain size than the ones with small grain size.
