自由地下水の水面解析について ―明きょ排水の水理について(3)―

Abstract

A two-dimensional approach to the unconfined groundwater flow from the mountainarea or the river to the drainage channels in the alluvial fan is discussed here. Thetwo-dimensional situation for the flow is based on the assumption that the basin may bedivided into several basins of rectangular shape, each bounded with a drainage channelon two parallel sides, and that the ratio of both length and width to depth from a freesurface to a sloping impervious base is so large that the vertical changes of the hy-draulic characteristics of the seepage flow are negligible.The fundamental equation has been developed for the unsteady flow, and some ofthe hydraulic significances of the parameters included in this equation have been discussed.For the purpose of making clear the fundamental characteristics of the flow, a solu-tion of the steady flow equation is first obtained with the technique of the numericalcalculations, and the effecta of seepage flow into a ditch are especially examined.Secondly, to obtain the analytic solution of the steady flow equation, the followingtechnique has been discussed by referring of the characteristics of the flow obtainedwith the above mentioned numerical calculations as follows: the seepage flow in therectangular region may be divided into both longitudinal and lateral flows which meanthe parallel and orthogonal flows to the drainage channel respectively, and both flowscan be related with the recharge elements which are defined as the difference betweeninflow and outflow through the section in unity width at any point in the longitudinalflow.Finally, the results obtained in this analytic method have been tested against thenumerical results.