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Typical Underwater Tunnels in the Mainland of China and Dec 01 2022· 1 Introduction China has ∼18 000 km of land coastline and ∼14 000 km of sea island are more than 11 000 islands in China of which 6536 have over 500 m 2 area each and 455 have residents Due to the restraints caused by the numerous bays and straits the economic …