A Simple Automatic Falling Head Permeameter

Abstract

The usual method of measuring the permeability of a homogeneous soil in the laboratory is a constant head or a falling head test. Of the two methods, the falling head test is more suitable for measuring the permeability of homogeneous clay as very small flow quantities are involved. The proposed method is to keep the conventional falling head test unchanged except to measure the falling head automatically through a very accurate differential pressure transducer. The low pressure end of the transducer is opened to the atmosphere to correct for changes in the atmospheric pressure over the 24 hour duration of a typical permeability test. By means of several repeated falling head permeability tests at different initial heads for the same effective stresses, it is demonstrated that reasonably reliable and repeatable measurements of permeabilities of clay can be made, provided that the applied head difference as a proprtion of the current vertical stress is swelling is induced by the seepage head.