雨水の鉛直浸透に関する実験的研究

Abstract

The infiltration phenomenon is one of the most important processes in hydrologic cycle. Inorder that rain water infiltrates into the ground in unsaturated state, it is necessary that aportion of bulk of air in void of soil or sand is compressed or exchanged by the penetratingwater, because generally there is a groundwater surface or a rock surface underneath the soil orsand stratum. Therefore, the behaviour of the air, in addition to capillary and gravitationalpotentials, is to contribute greatly to the infiltration phenomenon. This paper describes such abehaviour of air during the period of rain-water penetration into unsaturated sands and itscontribution to the infiltration. It is disclosed, as the results obtained experimentally, that ( 1there is a criterion for water ponding on the surface of porous stratum, ( 2) the exchangeabilityof air and water changes largely in this criterion, ( 3 ) a heavy rainfall over the criterionforces to compress the air in sand void, and (4), in the case of existence of groundwatersurface, the air is confined into the regions just under the sand surface and just above thegroundwater surface.