In dredging and reclamation, self-weight consolidation of marine clay need relatively long time. In this study, to accelerate self-weight consolidation time laboratory large size column test were performed using prefabricated vertical drain board. And also presented optimum time of prefabricated vertical drain board insert. Prefabricated vertical drain board-test result showed l/2 time to consolidation compared to Selfweight consolidation-test. Therefore, It can be judged that in reclamation of dredged marine clay, prefabricated vertical drain board can used to accelerate self-weight consolidation.
In present, rubble or earth and sand have been used to make a new site by reclamation. However, great amount of material needed for offshore reclamation, thus in most case insufficient material substituted to dredged marine clay near the reclamation site. A general unifying theory can describe sedimentation in a suspension and self-weight consolidation of the resulting deposit. Sedimentation is the process of particles settling in a suspension. The deposited particles form a sediment bed, a saturated soil layer, on the bottom of the fluid column. Consolidation is the time dependent compaction of the soil skeleton as a result of a load. Artificial ground that filled up with dredged material having high water content form a extremely soft ground, thus form a slurry phase ground with little bearing capacity. Stabilization of ground is inevitable to use as artificial island and landfill area. Long period needed to reach stabilized phase after self-weight consolidation and large settlement occurs during stabilization. In some cases, therefore, embankment with geotextile performed during self-weight consolidation due to limitation of contract period. When the dredged slurry poured into reclamation area, consolidation by self-weight occurs with drainage of excess pore water that existing in dredged soil and its rate depend on dissipation rate of excess pore water pressure and thickness of reclamation layer.
