Effect of Envelopes on Flow Pattern Near Drain Pipe

Abstract

Movements of soil particles in the vicinity of the drain lead to mineral clogging of drain pipes. It is therefore of high interest to analyze water flow patterns near the pipe in order to understand these movements. Two types of laboratory models have been designed: a rectangular sand tank with a central drain; and a simplified set‐up, the permeameter, which allows a one‐directional flow. The permeameter tests are directly derived from sand‐tank experiments, where the highest values of hydraulic gradient due to upward vertical flow occur below the pipe. The permeameter is a simple device designed for submitting soil cores to these unfavorable up‐flow conditions. Such a practical test is able to diagnose mineral clogging hazards and to help choosing a proper envelope material.