Electrically induced deformations of a bentonite slurry

¹ KLS Gogte Institute of Technology Belgaum, Belagavi, Karnataka, India
² CERIS/ Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Dewatering of soft clayey soils through Electrokinetic Treatment (EKT) is explored in several engineering applications. Hydrodynamic consolidation, a hydro-mechanical coupled mechanism, is now a electro-hydro-mechanical one, in which the total flow of fluid extracted is due to the superimposition of hydraulic and electrical gradients. Oedometer tests were performed in modified cells to study the effects of electrical current on deformations, measured for different vertical stresses. Instantaneous volume changes caused by electrical current were investigated on samples of consolidated slurries of bentonite, and during 3 cycles of EKT. In all cases constant electrical potential was applied after more than 90% of settlement had occurred, to distinguish electrical from mechanical effects. The same stress paths were applied in tests performed without electrical potential, for comparison. It was observed that the sign of vertical deformations occurring during the application of EKT depended on the confinement stress and soil initial state (swelling observed for stresses below yielding stress and settlements for stresses above this value). The deformations tended to stabilize after the application of EKT. In addition, secondary consolidation settlements have increased under the application of electrical current stresses, suggesting that electrokinetic flow is associated to microstructural water flow. The double layer repulsion theory was used to analyse the changes in deformation in the soil. This simplified analysis allowed to find interesting conclusions which contribute to understand the electro-hydro-mechanical phenomena occurring in bentonite during EKT.