Experimental study on electro-osmotic conductivity of Hangzhou sludge

Soil electrical conductivity has been extensively investigated in the fields of precision agriculture, geophysical mapping, and soil property mapping. However, the understanding of soil electro-osmotic conductivity is currently limited. Comprehensive insight into soil electro-osmotic conductivity is crucial for an accurately designing the electro-osmosis technique, which is widely accepted as a highly promising method for disposing soft soils with high water content. To fill this knowledge gap, a series of laboratory experiments was conducted using Hangzhou sludge. Four factors, including electrode material, potential gradient, soil water content, and pore water salinity, were investigated in terms of their influence on electrical conductivity of the electro-osmotically treated soil. Results show that during the electro-osmosis process, the soil electro-osmotic conductivity initially slightly increases and then decreases. The impact of electrode materials on soil electro-osmotic conductivity was minimal, whereas a high potential gradient was observed to generate low soil electro-osmotic conductivity. Furthermore, this conductivity was found to be linearly correlated with real-time water content. The slope of the correlation was also significantly influenced by the initial water content of the soil. Under different levels of pore water salinity, the soil electro-osmotic conductivity first increases to a peak and then decreases to a residual value. The soil electro-osmotic conductivity are observed to have a linear relationship with pore water salinity. These implications are closely linked to the soil conduction mechanism. Based on the foregoing findings, limiting the calculations to the pore water-induced conduction during the main stages of the electro-osmosis process is recommended. Furthermore, linear predictive relationships between soil electro-osmotic conductivity and the corresponding level of soil water content as well as between the soil electro-osmotic conductivity and the pore water salinity should be used in simplified calculation of the electro-osmosis process. The parameters involved in these relationships can be accurately determined through laboratory experiments.