Volume 23, Issue 2 (June 2000)
An Electrokinetic Testing Apparatus for Undisturbed/Remoulded Soils under In-Situ Stress Conditions
In this paper, the design and construction of an apparatus for the study of electrokinetics are presented in detail. The apparatus is capable of both applying a designated effective stress to a soil sample and measuring the volume change and pore pressure during the electrokinetic testing. The results of a high voltage electrokinetic test on a remolded natural clay sample are reported to illustrate the operation of the apparatus and to study the mechanism of high voltage electrokinetics. During the 91 day test period of, including the application of a high voltage (−10 kV to −12 kV) for 51 days via insulated electrodes, the volume and pore pressure changes were negligible. Nevertheless, the geotechnical properties of the soil significantly improved, including increases in shear strength (69%), shear modulus (151%) and preconsolidation pressure (700%). Since the increases are calculated with respect to the control sample under identical effective stress and drainage conditions over the same time period, they can only be attributed to high voltage electrokinetic effects, possibly cementation bonding, diagenesis, and ionic diffusion.
The electrokinetic testing apparatus developed in this study provides a viable tool for the study of electrokinetics on clayey soils for better understanding of the mechanisms involved in the process.