Coefficient of Permeability from AC Electroosmosis Experiments. I: Theory

Abstract

Electroosmosis techniques have been used in geotechnical and geoenvironmental engineering applications. However, due to electrochemical changes and gas generation at the electrodes as a result of prolonged application of a direct current electric field, its application in determining soil properties has been limited. A methodology, which uses a weak alternating current (AC) as the driving force is developed to minimize these adverse effects. The governing partial differential equation for one-dimensional AC electroosmosis is presented for an experimental situation in a companion paper. Three boundary conditions, which reflect the possible range for a closed boundary are identified. Transient and steady-state solutions are given for the ideal undrained boundary conditions. Analytical steady-state solutions are given for the two nominally undrained boundary conditions. These solutions indicate that both small deformations of the boundary cavity and impedance effects due to relatively low permeability of an equivalent porous stone play an important role in the pore-pressure responses. Procedures based on the steady-state solutions for backcalculating the coefficient of permeability are presented.