Large Steel Cofferdam Overall Floating Transport Anchor Pier Positioning Construction Techniques

The background of this text is the foundation of pylon P2# of Wuhan Tian Xin Zhou major bridge. It systematically studied the large scale steel suspending cofferdam design and building, sinking and integral floating technique, anchor pier location system and cofferdam location construction technique, cofferdam lowering and rising technique, piling work and cofferdam bottom sealing technique. Main work and innovations are:1. It brought out anchor pier location technique of large scale steel suspending cofferdam, which means that make use of anchor pier plus prestress strand location system to locate steel cofferdam. Comparing with traditional barge anchorage technique, it possesses remarkable features which are economical, quick and precise.2. The disadvantage that, for traditional suspending cofferdam, once it is located can not go up and down any more was broken through. Lowering and rising technique of large scale steel suspending cofferdam was initiated. It makes cofferdam going up and down with the change of water level during construction, and it's favorable to flooding prevention. Construction progress is speeded up greatly, and investment can be saved also.3. For the foundation work of pylon P2#, a whole set of construction design and calculation was accomplished which includes steel suspending cofferdam design and fabrication, integral floating and location technique, piling work construction and cofferdam bottom sealing technique and so on. Relative methodology was brought out systematically, and was applied successfully.4. The fruit of this text which was applied to Wuhan Tian Xin Zhou major bridge has fully presented its fast and precise location features. Its location precision reaches at: relative vertically < 1/2000; longitudinal and transversal direction < 30mm, diagonally torsion < 20mm. More than one month schedule has been saved, and the direct economic benefits is more than￥10 million, economical and social effect is outstanding. 5. This fruit is mainly applicable to the drilling pile and the high-pile pile cap foundation construction of super major bridge engineering, of which the site is in deep water as well as the reach where the geological situation is complex and the tidal reach where the stream direction changed often. It can increase the integral location precision of steel suspending cofferdam, reduce the driven gradient of steel casing, and also can strengthen the anti-flooding capacity with preset pulling force during flooding period, to ensure normal construction. Making use of the self-floating function of cofferdam, and according to the change situation of water level during construction to adjust the elevation of cofferdam, finally to achieve uniform construction in spite of in dry season or flooding season.A new technique/methodology has been summed up from the fruit of this text which is applied to the piling work and high-pile pile cap foundation construction of super major bridge which is seated over deep water and the reach where stream direction changes often. This new methodology is just the technique fruit of high-pile pile cap foundation construction with large scale steel suspending cofferdam by integral floating and anchor pier location. This fruit has already gained Technology Advancing First-class Rewarding of Chinese Railway Major Bridge Engineering (Group) Co., Ltd. The large steel suspending cofferdam integral floating and anchor pier location construction technique has gained National Invention Patent.