Electrokinetic wave phenomena in fluid-saturated granular media

Abstract

Electrokinetic (EK) phenomena in sediments arise from relative fluid motion in the pore space, which perturbs the electrostatic equilibrium of the double layer at the grain surface. We have developed EK techniques in the laboratory to monitor acoustic wave propagation in electrolyte-saturated, unconsolidated sediments. Our experimental results indicate that as an acoustic wave travels through electrolyte-saturated sand, it can generate electric potentials greater than 1 mV. A careful study of these potentials was performed using medium-grain sand and loose glass microspheres for a range of pore fluid salinities and ultrasonic frequencies. Experimental results are also shown to compare well with numerical and analytical modeling based on the coupled electrokinetic-Biot theory developed by Pride (1994).