Effects of electro-kinetic coupling on the measurement of hydraulic conductivity

Hydraulic conductivity is the proportionality constant relating the volume flow rate of a fluid through a porous medium to the imposed hydraulic gradient. Hence, there should not be any gradient or driving force other than a hydraulic gradient imposed on the sample during the measurement of the parameter. However, no precaution is taken to prevent the development of a streaming potential during the experiment. As a result, an electrical gradient is always generated across the sample and the measured hydraulic flow volumes are actually induced by the combined hydraulic and electrical gradients. The effects of electro-kinetic coupling are more pronounced in fine-grained soil. Moreover, the measured conductivity coefficient cannot be used in coupled flow equations to quantify the hydraulic volume flow rate contributed by the hydraulic gradient without appropriate corrections. This paper attempts to present the results of the theoretical analysis and experimental evaluation of the effects of electro-kinetic coupling in the measurement of hydraulic conductivity.