Key Role of Reclamation Analysis from Repository Planning to Acceptance Management in Disposal Pond for Dredged Clay

In Japan, environmental concerns have made it difficult to construct new disposal ponds for dredged clays. Therefore, in order to maintain continuous navigation, dredging plans and acceptance management should consider the current capacity of disposal ponds and predicted future trends. In this paper, a detailed sedimentation prediction method from the repository planning stage to the time of dredged clay acceptance and management during operation is investigated using a reclamation analysis developed from the generalized consolidation theory. In order to perform this reclamation analysis, consolidation parameters related to the compressibility and consolidation rate of dredged clay under low confining pressure are required. We therefore propose a method for determining consolidation parameters and also a method for predicting the amount of dredged clay to be received at various stages. In the repository planning stage, these coefficients, determined from the liquid limit of the clay and the results of tests on several dredged clays in Japan, were applied as initial values of consolidation parameters. In the subsequent phase of accepting the dredged material, the values identified from the back-analysis using the changes in sediment surface elevation over time and the water content distribution of the sedimentary clay layer were applied as modification values. Thus, by setting the consolidation parameters, this dredged clay reclamation analysis can be effectively used for a wide range of tasks, from sediment disposal pond planning to acceptance completion prediction.