斜面透水層中の浸透流

Abstract

Ground water flow may be generated in sloping soil layer laid on semi-pervious rock surfacewhen the infiltration of rain water I throughout the soil layer exceeds in the downward leakage ofwater L Out of bed rock surface. The author investigated theoretically the development of sucha flow due to the infiltration under semi-infinite region of rainfall in the ease where the bed rocksurface is fiat with a inclination b≡tan β to horizontal plane and the soil layer has a porosity a, permeability k and an uniform vertical thickness D and found an uniform flow which is coveredby two free surfaces; the one stretching downstream from upper limit of leak surface with a constantinclination cm tanr to horizontal surface and the other growing upwardly at a constant rate(I-L)/ σ in parallel with the bed rock surface. This flow exists within the limit of conditions1 -I>(1-I) (1 -tan2β/2) and I>l, where I≡l/k and l≡L/k may be called the specific infiltrationand leakage, respectively. In the case where 1-I= 1 -tan2β/2, then r =β/2. The frontalline of steady free surface will seep at the position in the distance S= UD sec β/(I-L) (U: horizontalDarcy's velocity of flow) downwardly along sloping soil surface from the fringe of rain-fall regionat the time T= σ D/(I-L) after the wetting front of the infiltration reached the bed rock surface.