Optimization Of Mooring System For Large Offshore Floating Island

Maldives lacks land.It belongs to atoll terrain,and the water are deep inside and outside the atoll.The construction of filled artificial islands is difficult in Maldives.To develop the large floating artificial islands is a feasible way to expand the urban land area in Maldives.The floating artificial island is an important structure,and often used as a hotel.The floating artificial islands are often subjected to wind,wave and current loads,so that the displacement of floating islands should be controlled within a certain range under the normal sea condition.As the same time,floating islands should be stable and safe under extreme sea condition.Therefore,how to design a reasonable mooring system to controll the movement and displacement of floating islands and ensure the safety and stability is the key technical problems for the construction of floating artificial island at sea.This paper based on the construction of offshore floating artificial island in the Maldives atoll sea area,It uses the numerical simulation method to study the mooring system scheme of large offshore floating artificial islands.This paper first analyzes the normal and extreme sea conditions of the Maldives atoll sea area,calculates the maximum environmental load of the floating island in various extreme sea conditions by using Orcaflex software,and primarily designs seven kinds of floating island mooring system schemes,and then the mooring effect of these mooring schemes is numerically simulated.The research contents and conclusions are as follows:(1)The environmental loads of different extreme sea conditions are compared.The results show that the extreme wave height and normal current have the largest environmental loads on the floating island,and this extreme sea condition is chosen as the sea condition of the 100-year sea area.(2)Under the working sea condition for two years,the mooring effect of seven layout schemes was analyzed under the three directions of normal wave of 0 degrees,30 degrees and 60 degrees wave direction,and the positioning effects of the seven mooring systems on floating islands are studied respectively.The motion displacement of the floating island and the maximum tension of mooring cable under the coupling action of seven mooring systems are compared.This paper is also analyzed the motion displacement of the floating island and the maximum tension of mooring cable when the mooring system in the most unfavorable sea state breaks.The results show that Scheme 1 and Scheme 7 have better constraint ability and mooring safety.(3)Taking the environmental conditions of extreme sea conditions,Analysis of safety and stability of two optimized mooring schemes.The results show that under extreme sea conditions,the safety coefficients of Scheme 1 and Scheme 7 are greater than 1.2 under extreme sea conditions.