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层次性土壤在自然界有广泛的分布。本文采用土柱法研究了两层性土壤的持水性能。实验结果表明,细粒土壤下垫有粗粒土壤时,上部细粒土壤的持水能力有明显的提高,可以超过最小持水量而得到若干补充水量。两层土壤孔隙的大小相差愈大,此种补充水量愈多。如里壤土被中砂垫底,上部155厘米厚土层可增加97-198毫米水量;被轻壤垫底,只增加30毫米水量。如土层排列相反,粗粒土壤被细粒土壤垫底时,则各自保持自身固有的持水能力。实验还表明,空气-土质界面对提高土体持水能力的作用相当于地下水位所起的作用。在邻近空气-土质界面之上,水分处于饱和,整个土柱剖面水分分布类似地下水位之上的毛管上升带一样。
Hierarchical soil has a wide distribution in nature. Soil column method was used to study the water holding capacity of two-layer soil. The experimental results show that when the coarse-grained soil is padded with fine-grained soil, the water holding capacity of the upper fine-grained soil is obviously increased, and the amount of supplementary water can be obtained beyond the minimum water-holding capacity. Two layers of soil pore size difference between the larger, the more this additional water. If the soil is sand bottom soil, the upper 155 cm thick layer can increase the 97-198 mm of water; the bottom of the light soil, only an increase of 30 mm of water. When the soil layers are arranged in opposite directions, the coarse soil, when it is subsoiled by fine soil, retains its own inherent water holding capacity. Experiments also show that the effect of air-soil interface on the improvement of soil water holding capacity is equivalent to that of groundwater level. Moisture is saturated near the air-soil interface, and the water distribution across the soil column profile is similar to the capillary rise above the groundwater table.