BACK ANALYSIS OF RECLAMATION BY PUMP-DREDGED MARINE CLAY : INFLUENCE OF GROUND WATER LOWERING

Abstract

When pump-dredged clays are discharged into a pond, suspended soil particles settle loosely to create sediments, which subsequently consolidate due to their own weight over a long period of time. In planning the capacity of such a disposal pond, it is important to estimate the time dependent volume change of dredged clays during the reclamation process. As the land thus created is extremely soft, ground improvement work is necessary if there exists a further plan of utilising the land. Predicting the soil profile of reclaimed land is absolutely necessary for designing the ground improvement. In this paper the authors i) outline the 18-year reclamation history of the Kanda Disposal Pond, ii) introduce a program to analyse self-weight consolidation under fully submerged condition, iii) modify the program to represent the suction effect due to ground water lowering, and iv) verify the applicability of the modified program by comparing the calculated results with the measured data. A simple analysis under fully submerged condition cannot explain the record of an 18-year reclamation, even if various combinations of consolidation parameters are used. The code modified to include the suction effect successfully simulates the actual behaviour when the appropriate parameters concerning the suction are chosen.