| Zhoushan is adjacent to the Yangtze River Delta and urban agglomeration like Shanghai, Hangzhou and Ningbo, facing the Pacific Ocean, which has a strong geographical advantage. It is the maritime gateway and channel of the Yangtze River Delta and the Yangtze River Basin. Zhoushan sea area is vast which has a numerous of islands. It has a advantaged deep-water harbor, unique islands, many deep-water channels and deep-water anchorages. With the Yangtze River Delta economic integration continuous progress, Zhoushan location advantage has been increasing. With the Shanghai International Shipping Center Yangshan Port is completed, the Port of Ningbo-Zhoushan port integration, Zhoushan river and ocean combined transportation service center is in the process, the number of medium and large ships passing the Zhoushan sea area is increasing.This paper’s studied sea area is between West Bailian Island waters and waters Shrimp main gate Fairway. West Bailian Island is located in northwest Shrimp main island of Putuo District of Zhoushan City with superior natural conditions. But there are numerous reefs around West Bailian Island, and it’s dangerous when ships pass. In order to eliminate the influence of reefs for navigation, it was decided to clean up several reefs. Because the reefs was identified to sedimentary rocks, we decided to do reef explosion first and clean up slag reef construction process by cutter suction dredger and other equipment next. Because it’s inevitable to produce a high concentration of suspended sediment and influence the surrounding marine environment. And the flow field and underwater topography will change after reef explosion which may do some erosion and deposition to the surrounding waters. I use the tidal current numerical simulation to predict the suspended solids range and erosion situation. And this study will provide a theoretical basis for the environmental impact assessment of rock blasting and a reference for project feasibility. What’s more, this study has a really practical significance.Considering the combination of numerous reefs and complex tidal currents in the sea area of Zhoushan, this study develops a numerical model to simulate the transport processes of suspended sediments during the explosion and clearance of the reefs based on Delft3D. The main results and conclusions are as follows:First of all, the results of numerical simulation for suspended sediments present different features of the suspended sediments transport during the explosion and clearance of the reefs at different time of flood and ebb tides, including the sediments concentration and transport distance. Within Macro-Tidal Coastal Waters in which the mean flow velocity is 1m/s, the sediments produced by reef explosion will increase the concentration by 0.010kg/m3. The effect time for the surrounding area is about 0.5 hour and the scope is 200m downstream. On contrast, the influence of suspended sediments produced by reef clearance on the surrounding area is smaller, and the time is shorter. So in order to reduce the impact on the surrounding waters by suspended sediments, it is recommended that the reef explosions should be implemented during the slack tide, and reef clearance tide can be implemented at any time.Secondly, suspended sediments transport velocity strongly depends on the tidal current velocity, but has little to do with the source intensity. Also in many strong tidal waters with numerous reefs. The transport of the suspended sediments will slow down because of the influence of the vortex and tidal currents... |
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