The Falling Water Table in Tile Drainage—A Laboratory Study

Abstract

Abstract A sand‐filled tank 6 by 10 by 2 feet is used to study the distribution of hydraulic head and quantity of tile outflow during drainage. A null‐type tensiometer for making rapid measurements of the hydraulic head is described. The measurements of the transient phase of drainage known as the falling water table are compared to the theoretical development of Kirkham and Gaskell as well as Childs. The experiment demonstrates that the assumption used in the theoretical developments that the soil possesses a fixed drainage pore space leads to an incorrect solution. The shapes of the experimental water tables are similar to the theoretical shapes but the rate of fall is not accurately predicted by the theory.