IMPROVEMENT OF MARINE ENVIRONMENTS BY DREDGING AND CREATION OF MARINE PRODUCTION AREAS

摘要

Fishing ports and enclosed bays are characterized by low exchange of seawater, inflow of effluent from the surrounding area, and run-off from the fisheries industry. Uneaten feed from aquaculture builds up, causing mucking of the sea floor, and soft cohesive deposits accumulate. This degrades the enclosed water environments and causes a decline in depth of water that can hinder the movements of fishing boats and other craft. Currently, the disposal of untreated muck, soft soils, etc., into nearby offshore areas is prohibited, so it is important that some method can be developed to process and reuse these materials. This paper has provided information about the construction of a manmade island in a fishing port, associated environmental assessment, and field observations made using a model embankment to solve above problems. The following conclusions can be made from the present study: 1. The use of mixture of dredged soil and a cement-base hardening material is effective for constructing a manmade island on soft ground and recycling dredged soil. 2. The lateral deformation of the mooring wharf during the construction of the manmade island was increased by an increase in the lateral earth pressure induced by the fill dirt. 3. The deep cement mixing section, rubble mound and mooring wharf merged into one unit and rigidly inclined in a lateral direction. 4. The relationship between the surface settlement of the central part of the embankment and the maximum lateral displacement in the ground under the toe of the embankment slope appeared to be nearly linear, and construction was carried out in a stable state.