Electrokinetic Treatment of Fine-grained Soils with Chemical Enhancement Solutions

Abstract

The electrokinetic (EK) soil treatment method is a comparatively new technology. It is being investigated in some parts of the world as a feasible and practical in-situ soil remediation and treatment method. When the application of traditional ground improvement techniques (e.g. surcharge, preloading, etc) is not practical for a particular situation, innovative approaches such as EK technique can be considered. The principles of the EK treatment method involve applying a low direct current (DC) or a low potential gradient to arrays of electrodes inserted in the low permeable soils that cannot readily drained. The EK method is applicable to fine- grained soils such as clays, silty clays and clayey silts, possessing specific mineralogical properties, which are electrically and chemically active. When a DC electric potential is applied to the soil, it simulates migration of electricity, pore water, ions and charged particles across the soil, creating several complex mechanisms such as electrolysis, electro-osmosis, electromigration and electrophoresis, respectively. This technique can also be incorporated/ enhanced by introducing desirable non-toxic chemical stabilisers such as lime or saline solutions to the soil at the appropriate electrode. The combined effects of these processes together with various geochemical reactions alter the chemical composition of the soil porous medium and hence modify the physicochemical, mechanical and engineering properties of the soil. Although the EK technology has been proven to be applicable in many laboratory bench scale experiments and field tests, some complicated features such as electrochemical reactions and changes in soil properties are not fully understood. Therefore, there is a need to conduct this research for a better understanding of the improvements in problematic soils and the efficiency of this technology.