閉塞湛水浸透の機構に関する研究

Abstract

In this paper the mechanism of confined infiltration with ponding, especially the movement ofwater and pore-air in the quasi-saturated zone which developes in the neighbourhood of sand surfaceis discussed. In the experiments of ponding infiltration which are carried out by using dry sandcolumn in the cylinder with bottom plate, we have observed that pore-air escapes from sand surfaceintermittently. Although, strictly speaking, the infiltration phenomena are discontinuous, in thisanalysis such phenomena are considered macroscopically as continuous.First, by assuming that the movement of water and pore-air in a quasi-saturated zone obeysthe equation of Darcy's type, the transformed kinetic equation of water and the state equation ofpore-air which describes the relation between pore-air pressure at lower end of a quasi-saturatedzone and the depth of the zone are derived. These equation contain two parameters changing withtime, which are found out using the results of the experiments already reported.Secondarily, these equations, for a quasi-saturated zone, the equations of movement and con-tinuity of both fluids and the state equation of pore-air, for an unsaturated zone, are simultaneouslysolved the quasi-analytical method already reported. The comparison of the calculated results withthe observed ones shows a good agreement. It is concluded that the equations applied in thisanalysis are valid to describe the infiltration phenomena in a quasi-saturated zone and, accordingly, such an infiltration mechanism has been made clear.