REAPPRAISAL OF FLOW TO TILE DRAINS .1. STEADY-STATE RESPONSE

Most techniques used to analyse the flow of water to horizontal tile d rains fail to separate the external boundary of the water table from t he internal boundary of the tile drain. This is the first of a series of three papers which consider the correct formulation of the steady s tate and time-variant flow to tile drains. This paper is concerned wit h steady state conditions and provides important information about the correct formulation of tile drainage problems, especially the fact th at the drain is an internal boundary. Field experiments are quoted whi ch demonstrate the separation of the tile drains from the water table. A finite difference numerical solution to the full differential equat ion is developed with the drain represented as an internal boundary. C omparisons are made between conventional methods of analysis and the n umerical solution; reference is also made to layered and anisotropic s oils and surcharge pressures in the drains.