In the summer of 2013, we were appointed by contractor VolkerStevin as designer for the extension of Berth 9 at Felixstowe Container Terminal. The port needed 920m of quay so that it could serve a pair of 18,000 TEU vessels, each measuring 400m long and 15.5m deep. The Berth 9 extension involved construction of 190m of new quay wall and deepening of the entire berth to -18m chart datum, giving a retained berth height of 24.6m, or 25.5m allowing for overdredge.
In addition to the 190m berth extension was a 95m return wall and a 190m rear wall, foundations for the ship-to-shore gantry cranes, pavements, utilities and services associated with dredging and reclamation and a remote mooring dolphin. Full award was made to VolkerStevin in early summer 2014 and works were completed on site in autumn 2015.
The new front wall was formed of 2.56m diameter contiguous tubular piles to match the design on the existing quay. These piles were some 35m long. The seaward crane rail was again set centrally above the front wall tubular pile in a precast/in situ cope beam arrangement while the landward rail was set within a beam spanning between single tubular piles spaced at 5.4m centres longitudinally. The crane gauge between seaward and landward rails was set at 35m. The rear wall was formed of a combination of combi-wall and sheet piled wall to suit loading conditions. A central anchor wall, formed of continuous AZ24 sheet piles, was used to tie back both the front and rear walls.
“The principal technical challenge on this project was to design the new front wall – challenging in its own right – to match the performance requirements of the existing structure that was being extended,” explains senior project manager Peter Mallin.
“Loads put on to these structures are substantial and they create structural deflections under different load combinations – vertical and lateral. Berthing line and in particular crane rail alignment tolerances are tiny in comparison with the scale of the supporting infrastructure – here the specified installation tolerance on gauge between the front and rear rails was some +/-3mm – as it was on the existing quay. Designing new infrastructure to match the performance, measured in millimetres, of existing infrastructure, can be particularly challenging.”
The urgency to extend capacity at Felixstowe was particularly acute given the facility’s standing as the UK’s biggest and busiest container port, and one of the largest in Europe. The port handles more than 4M TEU and welcomes approximately 3000 ships each year, with a vast network of connections through road and rail.
“It’s a hugely competitive sector, with different ports vying for their share of traffic,” adds Peter. “Those that have existing commitments with shipping lines don’t want to lose them to a rival port in the same region or even within the same company. They have to balance the need to keep pace with the growth of ships, while using existing space as much as possible. It’s important to make sure nothing goes to waste, which is where we can really help as a consultancy.”