桃園地區的土壤多為第四世紀的紅土、礫石,由於紅土為較不易入滲之介質,紅土的顆粒較小且易吸附水分,更因為紅土在入滲過程中,因吸水膨脹以致堵塞土壤孔隙,隨著土壤的含水量漸趨飽和,使得土壤孔隙變小,造成入滲率在入滲過程中快速下降之現象。因此,本研究對於桃園紅土地區進行土壤入滲試驗,以探討紅土之入滲行為。 本研究首先分析紅土試驗場址土樣,求得試驗場址紅土之平均比重為2.61,單位體積中的乾土單位重為1.65g/cm3,紅土坋黏土比例約為四比六左右。其次經由實驗室滲漏儀試驗,得到紅土飽和水力傳導係數約為3.3mm/hr,並利用現地入滲試驗求得紅土最終入滲率約在4~5mm/hr之間,發現土壤最終入滲率略大於飽和水力傳導係數,分析應為現地入滲試驗較實驗室飽和水力傳導係數試驗多出了初始水頭勢能與土層吸水勢能所致。 最後本研究並針對Kostiakov、Mezencev、Horton三種不同入滲經驗公式進行桃園紅土入滲適用性分析,發現整體而言Kostiakov入滲經驗式較適合於乾燥土層的短時間入滲,故較不適用於桃園紅土。Mezencev入滲經驗式於桃園紅土入滲行為擬合相近,而Horton入滲經驗式於初始含水量較高之土壤入滲行為也有不錯的效果。
Most soil in Taoyuan area is laterite and gravel. Since the laterite is not the medium of infiltration, and it is small and easy to absorb water. During the infiltration process, the inflation causes the obstruction between soils. The more water of soil, the smaller of soil pore, and the infiltration rate drops dramatically. Therefore this research mainly focus on the soil infiltration experiment in laterite area. The beginning of this research analyzes the sample of laterite . The average weight of laterite in is 2.61, the unit volume of dry soil is 1.65g/ cm3 and the laterite silt and clay proportion is approximately 4:6. According to the lab leakage instrument experiment, the final infiltration rate is slightly bigger than the saturated hydraulic conductivity. the final infiltration rate more than deposit potential and capillary potential. In the end of this research, three different infiltration equation models Kostiakov、Mezencev and Horton were used to analyze the infiltration apply of laterite. Generally speaking the Kostiakov equation is better to be applied in short time infiltration especially for dry soil, so it is not appropriate to be applied to this research. The Mezencev equation has lots of similarity in laterite infiltration, and the Horton equation is also good for simulation of initial infiltration.