Experimental Evidences of the Strengthening of Dredged Sediments by Electroosmotic Consolidation

Abstract

Nowadays dredged materials are increasingly seen as a resource, and strategies and methodologies for their beneficial reuse are being developed throughout the world. When dealing with fine grained sediments, electro-osmotic treatment is very promising to this aim, being able to speed up dewatering and to remove contaminants. The paper presents the first results of an experimental activity started to get an insight on the ability of electric treatment to strengthen fine grained dredged soils. A special oedometer was adopted to this aim, capable of applying different combinations of mechanical and electric loads to the soil, and large enough to allow the final retrieval of specimens to be tested in a triaxial cell. Both the oedometric and the triaxial test results obtained on a soft dredged material at a very high water content indicate that the application of a low voltage produces a negligible volumetric reduction but a complete change in the mechanical behaviour of the treated soil. Upon electro-osmotic consolidation, the soil—still having a very high void ratio—behaves as being over-consolidated, with a brittle behaviour in the triaxial tests and a large increase of the yielding strength in the oedometric tests. It is argued that such a sharp change in the macro-mechanical response of the treated soil is not related to the amount of water removed but to the change in soil microstructure caused by the removal of part of the electrically bonded water during the electroosmotic process.