On the mechanism of soft clay being improved entirely in the ECT treatment

The objective of this study was to demonstrate that the clay strength can be improved significantly over the entire sample during electroosmosis simultaneously with the injection of 0.75 M CaCl₂ solution for 72 h, then 1.5 M KOH solution for 48 h, then Na₂SiO₃ solution for 72 h, and then injection of deionized water for 168 h. Such an improvement was significant in terms of the improvement strength and improvement area as compared with the previous studies in the literature that the clay strength was improved only near the anode or cathode while the areas between the electrodes remain weak. The mechanism of the improvement was also studied by examining the physical and chemical properties of the treated clay at each phase of treatment. The cone resistance, water content, pH value, and the Ca²⁺ concentration were measured at each phase. Results also indicated that the quality of the Na₂SiO₃ solution might degrade in the anode compartment during treatment because of electrolysis of water. However, it was found that such a degradation was not very serious, which would not influence the test results significantly. For simplification, it may not be necessary to replace the possible degraded Na₂SiO₃ solution with the fresh one.