For the design of foundations of offshore structures including gravity platforms, jackets, jack-ups, seabed systems, etc., steel piles or skirted foundations are often used. An important parameter affecting the design and cost of the foundation is the strength of marine clays. A new process to increase the strength of marine days has been developed using elelctrokinetic strengthening. An experimental program was conducted and the results showed that the strength, preconsolidation pressure and shear modulus of the marine clay were increased considerably using this process. This paper presents the design, execution and results of the electrokinetic strengthening experiments on a marine clay recovered from a land reclamation site on the Korean coast. The discussion covers practical issues such as layout of electrodes and prefabricated vertical drains, application of intermittent current, power consumption, monitoring of soil deformation and pore water pressure during treatment, and post treatment geotechnical, physical and chemical properties of the soil. The process developed in this research has the potential applications for new offshore structures as well as for rehabilitation of existing platforms under various loading conditions.
The application of direct or alternating currents in a uniform or nonuniform field, generates electrokinetic process including electroosmosis, electrophoresis and dielectrophoresis. Upon application of an electric field to clays and silts, consolidation and strengthening of these soils occur if the method of application is proper Iv designed and the electrochemical properties of the soil satisfy certain requirements. The earliest application of the electrokinetic method is electroosmosis by Casagrande (1948, 1949, 1952) in silts. Bjerrum, Moum and Eide (1967) employed electroosmosis to stabilize an excavation in a very soft Norwegian quick clay near Oslo. It was found that the average undrained shear strength was increased up to four folds.
