Study On Sediment Movement Of Muddy Seabed In Archipelago Waters

In China, due to reasons such as siltation available deepwater coastline has developed at the estuary and coast. There are many difficulties to transform the old harbors in our country at present. But the deep development of islands shoreline has a great potential for exploitation. Therefore the development to deep-water port coastline of archipelago waters will not only effectively relieve the contradiction between waterway transport demand and the port status but also be huge potential. Due to hydrological characteristics and landscape characteristics of archipelago waters are complex. Many problems need to be solved to the movement mechanism. So the study of dynamic characteristics, sediment problem of archipelago waters has great economic value, far-reaching scientific significance and widespread application prospect.According to the remote sensing data, field data, the laboratory experiment, mathematical model and theoretical analysis, the hydrodynamic force and sediment condition of archipelago waters are analyzed roundly, and the sea-bed nature, sediment transport form and sediment mechanism of archipelago waters are analyzed in detail. Based on the concept of equilibrium sediment concentration, the siltation index and forecasting mode of muddy seabed evolution is put forward. The prediction formula for siltation of marginal quay dock is established in the muddy seabed. The results show:(1) The tidal currents of the study archipelago waters belong to informal half-day shallow sea tidal current. Tidal current is reversing current. The tidal current velocity is very strong. Under the natural state, because the island is more, shoreline is complex, there are shunt, confluence and circulation obviously; the wave is weak within islands waters due to the action of islands shield; tidal current is the main dynamic force to sediment lift and transport; the tidal current strength determines the change of seabed sediment to a certain extent.(2) In archipelago waters, blocking branches plays an important role to the adjustment of water flow and smooth flow; as change of land boundary (that is, blocking branches), change of flow velocity show a discontinuous process of "part change-change extension-smooth and steady change-change enlargement"; the influence degree on main section tidal volume is increased gradually. After the land border reaches a certain form, tide power change tends to steady, if we continue to change the boundary shape, tide impulses to the adverse direction. (3) In archipelago waters, suspended sediment concentration is high. The seabed evolution is aroused by suspended sediment transport. In archipelago waters, sediment erosion and deposition of muddy seabed are mainly related to local sediment suspension, transport and sedimentation except the background sediment concentration. Suspended sediment concentration distribution in space and time are inhomogeneity prominently. Because, on the one hand, the sediment transport and diffusion of background sediment environment effects sediment concentration distribution, on the other hand, the "channel effect" between islands impacts sediment concentration distribution. In the waters, suspended sediment concentration shows two types--suspension pattern and settlement pattern.(4) Terrain adjustment (scouring or silting) are quickly by influence of land boundary changes within the waters. As the land boundary fixed, water stability and smooth, the terrain changes tend to be relatively balanced. Combination of seabed properties, sediment movement form etc., based on the sediment deposition mechanism and the relationship between actual sediment concentration and equilibrium sediment concentration, the seabed scouring or silting indicator is put forward in the islands sea areas. Further the model of seabed evolution is established. The model is validated based on physical model, mathematical model results. Taking the Yangshan Deep-wate port sea area as an example, the seabed evolution is forecasted using the the muddy seabed evolution model.(5) Improved of the methods to the index n value in the current continuous laws to the alongshore basin flow; in the basin, velocity and basin aspect ratio have good relationship under n value different conditions, which affect flow velocity and depositing change. The sedimentation prediction formula is established to the alongshore basin. The formula contains the n value. Taking the Yangshan Deep-wate port sea area as an example, the silting thickness is calculated to the first and second harbor basin waters using the prediction formula. This result is in good agreement with the measurement data. The error is about10%.