Albert Embankment Temporary Cofferdam 2
Robert West was appointed by the joint venture of Ferrovial Agroman Laing O’Rourke joint venture (FLO) responsible for delivering the central section of the Tideway project to design Temporary Cofferdam 2 at Albert Embankment on the River Thames. There are three linked cofferdams at Albert Embankment being built in stages.
The Temporary Cofferdam 2, located downstream of Vauxhall Bridge, creates a dry area to enable the construction of the Interception Chamber (part of the permanent works) which will intercept the flows from the Brixton and Clapham Culvert.
The Clapham Culvert is upstream of Vauxhall Bridge, a third Cofferdam is currently under design to intercept the flow and divert it to the Interception Chamber at Cofferdam 2.
There will be a tunnel connecting Cofferdams 2 and 1, where the main shaft is located.
Robert West also undertook CAT III checks on Cofferdam 1 and are designers for Cofferdam 3.
The cofferdam is located close to Vauxhall Bridge. This space restriction meant a typical cofferdam solution (such as those used at Chelsea and Blackfriars) would not be viable. The Robert West team provided a flexible solution of a cantilever structure with resistance from tubular piles embedded in the soil.
Within the cofferdam 2, two separate chambers have been created, one to temporarily divert the flow from the Brixton Culvert while the permanent works are constructed and the second to receive the tunnel from the Cofferdam 3 These chambers had to be built at different depths as the Tunnel becomes deeper to avoid Vauxhall Bridge. Design of these chambers was complex due to the fluctuating levels of water from different sources – that of the tide, and from the two combined sewer outfalls.
It was identified that the main piles of the northernmost wall were clashing with the future Connection Culvert (part of the Permanent Works). Therefore, the piles could not be designed to the required level to be a self-standing structure. Instead, a wall formed of sheet piles with a shorter embedment was proposed. To provide the additional strength required due to the lack of embedment and stiffness, two no. levels of wailing beams were designed to transfer the water pressure to either side of the Connection Culvert
A vibration assessment was undertaken for piles which would be placed close to the pier. The analysis guided our engineers to design shorter piles at key points.
As the cofferdam is shorter than the barges additional isolated piles were designed to provide the required berthing/mooring points for a safe manoeuvre.
Due to the proximity of the barges to the Vauxhall Bridge Pier, a protection pile was designed to prevent damage to the Pier during the approach manoeuvre of the barges.
Cofferdam 2 has now been completed and work progresses on Cofferdam 3.
Our designer enjoyed the opportunity to design retaining walls which required both structural and geo-technical elements.
To get an idea of the sheer scale of the project visit https://www.youtube.com/watch?v=JnhbUKOP7Fs