Construction method for steel sheet pile cofferdam on underwater exposed bedrock

The invention discloses a construction method for steel sheet pile cofferdam on an underwater exposed bedrock. According to the method, steel sheet pile cofferdam can be constructed without grooving the exposed bedrock on an underwater plane. A covering layer is formed through sand filling, a construction environment that the covering layer is formed underwater is built, then a conventional steel sheet pile cofferdam construction technique is adopted directly, and steel sheet pile cofferdam construction is finished. The work of formation of a mounting groove through drilling on the water surface is omitted, the construction cost is effectively reduced, the construction cycle of a project is shortened, and the work efficiency is improved; a basic covering layer for steel sheet pile positioning is formed through sand throwing and filling, the construction environment that a covering layer is formed on the exposed bedrock underwater is built, steel sheet piles are subjected to insertion and closure construction, and then steel sheet pile cofferdam construction is completed. The method does not require underwater construction of mounting grooves, the steel sheet piles are accurately positioned, the difficulty of the construction technique is small, requirements for equipment are reduced, and high-efficiency and high-quality cofferdam construction is realized.