Reappraisal of flow to tile drains I. Steady state response

Abstract

Most techniques used to analyse the flow of water to horizontal tile drains fail to separate the external boundary of the water table from the internal boundary of the tile drain. This is the first of a series of three papers which consider the correct formulation of the steady state and time-variant flow to tile drains. This paper is concerned with steady state conditions and provides important information about the correct formulation of tile drainage problems, especially the fact that the drain is an internal boundary. Field experiments are quoted which demonstrate the separation of the tile drains from the water table. A finite difference numerical solution to the full differential equation is developed with the drain represented as an internal boundary. Comparisons are made between conventional methods of analysis and the numerical solution; reference is also made to layered and anisotropic soils and surcharge pressures in the drains.