In-Situ Volume-Change Properties by Electro-Osmosis - Theory

The basic concept involves incorporation of a simple electrode system in a field probe, measurement of pore-water pressure changes at the electrodes as a function of time in response to a DC field, and measurement of the electro-osmotic flow rate of water. Mathematical solutions for pore-water pressure responses for different electrode geometry and drainage conditions at the electrodes are presented in dimensionless form, so that measurement of pore-water pressure responses at the electrodes as a function of time for a relatively short period should enable computation of the coefficient of consolidation, c_v and the ratio of the coefficient of electro-osmotic conductivity to hydraulic conductivity, k_e/k_h. Unique solutions for k_e, k_h, and the coefficient of volume change, m_v, are shown to be possible using measured electro-osmotic flow rate in a closed loop between electrodes and comparison with theory.