Huge Cofferdam Launch Solution

Airbag launching technology is especially good for temporary launch project because of its low demand of launch conditions. 

Huge steel cofferdams are fabricated for bridge piers construction, some of them weigh a few thousands tonnes that is difficult for floating crane to lift and install. 

By airbag launching people can easily send massive structure into water, the weight of cofferdam is not a problem for airbag launching. So people can fabricate cofferdams on the nearest site from its final installation position to save traditional water transportation cost and time. Also most construction work can be completed on the land that will surely improve fabrication precision and shorten delivery time.

 

Creates Cofferdam Bottom

Different from vessels and caissons, cofferdams don't have the flat bottom that can enable airbags to roll. We must create a flat bottom for cofferdam launch and do this preparation work before the start of cofferdam construction.

Steel plates are most often used to make the flat bottom of cofferdam. For cuboid cofferdam two plates can be place underneathe the two parallel edges. Width of steel plates are decided by the weight and structure of cofferdam. Generally steel plates need to cover less than half of cofferdam width.

 

For cylindrical steel cofferdams, support girders and brackets should be added to support the steel plate bottom. Those brackets and steel plates will be removed after the launch, so they are designed to be temporarily fixed.

Launch ramp

Most cofferdam launch ramps are compacted natural ground, some reinforcement measures may be employed to suit bearing capacity demand. Gravel layers and steel plates are convenient material to enhance the launch ramp.

Ramp slope angle demand is similar to ship launching. But the ramp for cofferdam launching is temporary and sometimes it is not highly reliable, its slope angle generally is designed to be bigger to achieve a quick launch. Also due to construction site limitation, the bigger slope angle is preferred by site crew.

Water depth of launch area should be one or two meters bigger than the cofferdam draft.

Holding system: Refer to ship docking and launching facilities

Cofferdam airbag launch solution is peerless for its cost effective and convenience. One 3000 tonnes cylindrical cofferdam with 56 m diameters and 20 m height can be assembled and launched with airbags in 45 days. In China the first cofferdam was launched with airbags in 2006 then the airbag launch method became into the prominent solution for huge cofferdams launch.

Reference: Ship launching airbags   Calculation of airbag ship launching  Heavy lifting and transport with airbags  Caisson transfer with airbags

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