Optimisation of Layout of Semi-enclosed Basin in Micro Tidal Region to Minimise Siltation for Mega Ship by FEM

Abstract

Many developing countries in the world are building infrastructures like roads, rails and ports at an exponential rate and India is not an exception. The infrastructures like berths/docks/quays are being built in India in estuaries/open coast to meet the growing demand for waterborne transport. Many shipyards have started building of mega ships and those situated in creeks/estuaries are augmenting their building/repairing facilities by increasing quay wall/constructing new docks to enhance their productivity. However, siltation is a menace in macro/micro tidal regions and shipyards have to deal with it. The shipyard in Ernakulam channel at Cochin (India) is free from waves, however, discharges from backwaters during monsoon, micro tide and shallowness along quayside with deeper gorge at centre of estuary attracts and traps the sediment in eddy at quayside. This causes heavy siltation of 3–4 m/annum and restrictions on dredging due to environmental laws disallows building of mega ships requiring 4–6 years berthing. Hence to overcome above crises, knowledge of hydrodynamics responsible for siltation, reliable estimation of siltation/annum and technique to minimise siltation is essential. The application of FEM to simulate complex hydro-morphodynamics based on site-specific oceanographic data for monsoon/non-monsoon, analysis of dredging data form the basis to evolve optimal layout of semi-enclosed basin for minimisation of siltation. The hydrodynamics and siltation rates observed in model are 90% in agreement with the prototype and basin configuration with three sheet piles minimises the siltation by 43%. Thus, FEM not only optimises the layout of basin for reducing maintenance dredging but also satisfies environmental laws promoting the building of mega ships.