閉塞浸透機構に関する研究 (2)

Abstract

The air existing initially in the void of soil is not free to escape, because it is needed to bedisplaced by the water falling as rains on the land surface. In order to disclose such mechanismof air-water exchange during ponded infiltration, the theoretical consideration was carried out.From the experiments of ponded infiltration into the column of dry sand, it was found that themoisture profile is formed by quasi-saturated and unsaturated zone, and, in the homogeneousfield, the former developes in the neighbourhood of the surface of sand and the latter followsthe former downwards.In order to clarify the mechanism of air-water exchange through the quasi-saturated zone, the ordinary differential equations were solved. These equations are obtained by combiningthe quasi-analytical solutions reduced already for the unsaturated zone with such assumed relationsfor the quasi-saturated zone that the movement of water obeys the law of Darcy's type and, forthe movement of air, the relation is given by the linear combination of the length of the quasi-saturated zone and the pore-air pressure at the lower end of such the zone. After comparingthe calculated results with the observed ones, it was found that both show a good agreement.Therefore, it was concluded that the above two relations assumed for the quasi-saturated zoneare meaningful and available.