Coupling of electrochemical and mechanical processes in soils under DC fields

Direct current (DC) electric fields have been applied in several geotechnical and geoenvironmental engineering applications, including electro-osmotic dewatering and consolidation, ion injection and contaminant removal. Such applications cause electrochemical effects in the soil, leading to changes in the soil's physical, chemical and mechanical properties. Some of these changes have been evaluated extensively (such as those occurring under electro-osmotic consolidation) based on the assumption that electrochemical conditions are uniform between the electrodes. However, recent studies have shown that nonlinearity in these conditions develop between the electrodes leading to changes in the chemical, physical and mechanical properties of the soil. This paper evaluates the nonlinear effects on these properties as measured in some specific applications. In particular, the application of DC fields to soft soils is shown to alter the soil in both its mechanical and physical properties. The soil's undrained shear strength is increased by interparticle cementation brought about by the electrochemical injection of ions into the soil under the DC field. In addition, soils can consolidate or swell under these fields. In both of these cases, the development of a nonlinear voltage distribution across the soil is clearly measured, and can affect the progression of any electrochemical soil treatment as well as the accuracy with which it is modeled. (C) 2003 Elsevier Ltd. All rights reserved.