Design And Construction For HuangGang Highway And Railway Transit Yangtze River Bridge Double-Wall Steel Boxed Cofferdam Of Main Pylon

The NO.2main tower pier foundation of WuGang inter-city railway HuangGang highway and railway transit Yangtze River Bridge locates in a position with conditions of deep water and rapid flow, river bed scouring effect, oblique rock surface, navigation interference, complex condition and difficulties of construction. The paper made design calculation for the double-wall steel boxed cofferdam of NO.2main pylon pier foundation and its anchor for the bridge, took a systematic approach to the research for construction method and process of the double-wall steel boxed cofferdam. The main research work and achievements are as follows:1. Design calculation according to the most unfavorable conditions for each constituent of the double-wall steel boxed cofferdam, including double-wall side panel, bottom keel, internal frame, bottom sealing concrete, positioning steel armor tube, etc, have been made, and points for attention of the construction process are put forward.2. Calculation for anchor system of the double-wall steel boxed cofferdam, including main anchor of the cofferdam, stern anchor, side anchor and positioning side anchor, etc, have been done. Matters of the number and tonnage of main anchor, stern anchor, side anchor and positioning vessel side anchor, the specifications and length of anchor chain and mooring line have been determined according to the calculation.3. A comparative systematic research have been made for construction method and process of the double-wall steel boxed cofferdam, every step of construction process are designed, including launching, floating and location of the cofferdam, inserting steel protect tube, construction of drilled pile, lowering and bottom sealing of cofferdam, etc; and detailed regulations about technological process have been done as well.The research results of the paper have been applied in the manufacturing and construction for double-wall steel hanging box of NO.2main tower pier foundation of huanggang highway and railway transit Yangtze River Bridge. Because of application of the research results, new Breakthrough of the construction technology about whole floating and precise positioning of double-wall steel hanging box was achieved, leaving less than5cm plane positioning error, less than1/1000and1/500perpendicularity errors of steel hanging box and steel protect tube respectively, so as to get valuable experiences about the construction techniques of deep water large foundations under complex conditions.