The application of electrokinetic geosynthetic materials to uses in the construction industry

Abstract

Electro-osmosis is one of the five electrokinetic phenomena that may occur in soils, and the phenomenon of principal interest to this thesis. It may be defined as the movement of the pore fluid in a fine-grained soil caused by the application of a DC electrical potential difference across the soil mass. One of the main reasons that electro-osmosis has not received a more widespread application in the field of geotechnical engineering is due to the difficulty of successfully applying the electrical potential field to the soil mass. This thesis addresses the technique of using a carbon filled polymeric electrokinetic geosynthetics (EKG) to apply the electrical potential field and induce electro-osmosis in a soil mass. The thesis reviews the historical development of geosynthetics and the different techniques available for making them electrically conductive are discussed. A new type of EKG band drain is introduced and its construction, durability and connection technology are presented. The application of electro-osmosis, through the use of the EKG band drain, to the functions of soft soil consolidation, cohesive fill to reinforced soil structures and the volume control of shrinking and swelling susceptible soils are considered. Design methods are developed for these functions and are applied to two full-scale field trials in the application areas of electroosmotically enhanced reinforced cohesive soil and electro-osmotic volume control of an embankment, and a smaller scale field trial of electro-osmotic consolidation of soft soil. The results of these field trials have been analysed with respect to the design methods developed and confirm their validity for future use. Soil acceptability criterion have been developed to allow the applicability of electro-osmosis, to a soil to be evaluated based upon conventional and electro-osmosis specific soil mechanics laboratory tests. Potential future applications for electro-osmosis and EKGs are suggested.