Two circular sheet-piled cofferdams built in the River Medway provide a piling platform for the main bridge span on High Speed 1
A cofferdam (or caisson) is a type of watertight construction designed to facilitate construction projects in areas that are normally submerged, such as bridges and piers. A cofferdam is installed in the work area and water is pumped out to expose the bed of the body of water, so that workers can construct structural supports or perform other types of work in a dry environment. The most basic type of cofferdam (as here) uses sheet metal, which is pounded into the bed of the body of water to create a watertight wall. The viaduct carrying the High Speed 1 (Channel Tunnel Rail Link) over the River Medway estuary near Rochester in Kent is a uniquely styled bridge. The km long, 25-span pre-stressed concrete box girder viaduct has become a symbol for the new railway and the 152 m main span has extended the limit for high-speed train crossings. It was required to sit comfortably in its river environment and together with its two companion road bridges for the M2 motorway. The viaduct’s design was approved by the Royal Fine Arts Commission and received the Concrete Society Award for Civil Engineering in 2002. Building the bridge presented some complex engineering challenges. Concrete sections of rail-bed 40 m in length and weighing 1000 tonnes were assembled sequentially in a launch area on either side of the river, then gently slid on stainless steel bearings to be fixed on top of piers spanning the river banks. Pairs of 900-tonne capacity hydraulic jacks were used pushed the sections into place. The main span across the estuary itself was constructed as two balanced cantilevers arising from piers in the River Medway.
Size: 3314px × 3313px
Location: Medway Estuary, Kent, UK.
Photo credit: © qaphotos.com / Alamy / Afripics
License: Licensed
Model Released: No
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