Electroosmotic and hydraulic flow rates through kaolinite and bentonite clays

The objective of this paper is to discuss the effects of electrokinetics on the rate of flow of water through some low permeable clay soils. Experiments were carried out on test specimens prepared by compacting commercially available kaolinite and sodium bentonite clays. Using falling head permeability tests, hydraulic conductivity values of these clay soils were determined. Subsequently, the experiments were repeated under different electric gradients to assess the effects of electrokinetics on the rate of flow. The flow characteristics were evaluated using the rate of electroosmotic flow of water Q_e (cm³/s), coefficient of electroosmotic permeability k_e (cm²/V/s), coefficient of water transport efficiency k_i (cm³/Amp/s). The test results suggest that the rate of flow of water through low permeable clay soils is significantly increased by some orders of magnitude due to the application of a direct current. This flow increase appears to be more pronounced for clays that have lower hydraulic conductivity values. It is noticed that electroosmotic permeability is independent of clay type while the voltage gradient has minimal effect on electroosmotic rate of flow for the tested clay soils.