Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Dielectrophoresis, the action of a strong, non-uniform electric field on particles, is potentially a new technique for soil improvement. The principles and technical implementation of dielectrophoretic strengthening of natural clays were investigated in this study. The research included two aspects: the theory of dielectrophoresis in clay-water-electrolyte systems and the experiments of dielectrophoretic treatment on natural clays.;The dielectrophoretic force imposed on a clay-water-electrolyte system is determined by the configuration of the non-uniform electric field and the effective polarizability. The direction of the dielectrophoretic force is governed by the effective polarizability that is in turn controlled by the permittivity and conductivity of the clay-water-electrolyte system.;In the experimental program, the effects of dielectrophoresis on two natural clays recovered from Ottawa, Canada were investigated. An electrical potential difference in the order of 15 kV was applied on the clay samples through the insulated electrodes. It was found that the effectiveness of the dielectrophoretic treatment was related to the magnitude and intensity of the electric field intensity. Under different electrical field configurations, the overall soil strengths increased up to 44.0% after 28 days of treatment. The sensitivity of the clays was reduced up to 70%.;A comparative study was also conduced to examine the effects of dielectrophoresis and electro-osmosis in the clays. The characteristics of the two methods were discussed.;The dielectrophoretic process is efficient on energy and the electro-chemical reactions associated with the electric current are eliminated. Consequently, the impact to the environment in the process is minimum.;The dielectrophoresis technique may provide potential solutions for the improvement of soft, sensitive clays, consolidation of slurries, remediation of contaminated soils and water, and other applications in geotechnical and environmental engineering based on the findings in this study.



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