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Bristol Castle bridge
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Technical specifications
Restrictions... and solutions
The original scheme was for multiple mini piles installed from within sealed cofferdams. The space restriction limited the size of available pile diameter, and this severely limited the horizontal load capacity of the foundation.
Access to the site was only available by barge, from a landing station half a mile upstream from the site, under several low lying bridges.
Martello proposed a solution to replace the multiple mini piles with 750 mm diameter piles using a technique developed at Leeds Station, and thereby negating the necessity to install cofferdams prior to piling.
Initially a 900 mm diameter Caisson was installed by the rig through the dock and into the underlying firm material, then 750 mm diameter casings were installed through any unstable material and the pile bored to its founding depth. The reinforcing cage (full depth) incorporated a permanent thin-gauge steel liner attached to the top of the cage to provide a shutter to contain the concrete and lift the concrete up, and out through the water.
This technique allowed the contractor to save program time, and make use of the completed pile to provide a support system for his following temporary works to form the concrete piers.
Linking modern to ancient
The stylish curved bridge is 92 m long and 4 m wide. Its sinuous shape was designed to maximise the length of the structure to allow the minimum gradient on the bridge from either side, while maintaining the necessary clearance over the navigable section of the watercourse.
The bridge links Finzels Reach, the new fashionable development of Bristol, to Castle Park and the remains of the 900 year old Bristol Castle.
The dock being located in a fashionable part of Bristol, noise restrictions would apply to the project, restricting the use of heavy hammer driving equipment.
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