Dry-dock-free underwater shallow-buried open-cut large channel basic structure unit and construction method

The invention relates to a dry-dock-free underwater shallow-buried open-cut large channel basic structure unit and a construction method. The basic structure unit used in the method has the following characteristics that the length of each basic structure unit is 20-25m, a sealing door is arranged at one end of each basic structure unit, the other end of each basic structure unit is of an open structure, and a drainage pressure relief valve is arranged at the lower end of each sealing door; a rubber water stop belt is arranged at the end of each basic structure unit in a surrounding mode, and a floating and ballasting cabin capable of adjusting the water inlet and drainage capacity is fixed in each basic structure unit; and at least four axis positioning foot stands are arranged at the bottom of each basic structure unit. The channel basic structure unit can be directly prefabricated on the flat ground, a large temporary dry dock does not need to be built, the temporary engineering investment is reduced, the