Experimental Study of Electro-Kinetic Dewatering of Silt Based on the Electro-Osmotic Coefficient

The electro-kinetic technique, which involves a direct electric current within porous media, has been studied extensively and applied in many areas. The technique is considered a promising method to dewater soil. However, uncertainty still exists as to the electro-osmotic coefficient, which is of great significance to the electro-kinetic dewatering effect. Therefore, the effective electro-osmotic coefficient and total electro-osmotic coefficient have been distinguished in this article. Influence of external factors (electric potential gradient, electrode material, and electrode spacing) and internal factors (initial water content, types of electrolytes, salt content, and humus content) on the electro-osmotic coefficient were investigated by laboratory experiments with Hangzhou silt. Results demonstrate that the external factors had a significant impact on the total coefficient but little influence on the effective coefficient. Internal factors such as initial water content, salt content, and humus content of the soil were found to have considerable impact on the effective coefficient whereas no obvious effect was noticed for varied electrolyte types. Moreover, critical values of the initial water content, salt content, and humus content were highlighted for the effective coefficient. The trend of the effective coefficient with a certain factor varies when the factor is within or beyond the critical value. As for the Hangzhou silt that was studied, critical values of the water content, salt content, and humus content were suggested to be between 70% and 79%, similar to 0.5%, and between 10% and 20%, respectively. The electro-osmosis technique is believed to be inapplicable for soils with water content less than 70%, salinity higher than 2%, or humus content higher than 20%. The results obtained can provide guidance for evaluation of the applicability of the electro-osmosis technique.