ANALYSIS OF AN ELECTROFORCED SEDIMENTATION OF HIGHLY CONCENTRATED CLAY SLURRY IN CONSOLIDATION REGION

A gravitational settling rate of highly concentrated slurry in which t hickening proceeds due to consolidation mechanism is greatly enhanced by applying a D. C. electric field. Consolidation starts from the bott om of sediment and propagates upwards but an abnormally strong consoli dation also takes place in an upper portion of the sediment. The basic differential equation for such electroforced sedimentation is derived by use of Kobayashi's equation which describes a now in a porous mate rial under an electric field. The relation among local hydraulic exces s pressure, solid compressive pressure and gravitational force on soli d particles is also obtained. Based on the theory, the larger the poro sity of sediment the greater the flow rate of electroosmosis; the elec troosmotic flow at the settling surface is accordingly the largest amo ng those at any layers in the sediment. An abnormal compaction of the layer near the settling surface is consequently due to the difference between flow rates at the surface and any layer under the surface, The theoretical change of porosity distribution and sediment height with time of Mitsukuri-Gairome day compares favorably with experimental obs ervations.