Quinn Piling has been carrying out major piling works at 12 Quays Ferry Terminal in the Wirral dock in Birkenhead, UK, for Stena Lines ferry routes connecting Merseyside with Northern Ireland. The scheme will allow the dock to accommodate larger capacity ferries with Stena Line's new E-Flexer RoPax vessels which are now under construction in China due for delivery in early 2021.
The piling works are required to support a new fixed bridge along with an upper deck extension to the existing floating pontoon to allow use of a new one-way roll-on/roll-off access road with increased vehicle handling facilities.
Piling works started for the principal contractor Farrans, on behalf of Peel Ports & Stena Line, in July 2019 with the arrival of two jack-up barges, the SeaSeven and Seariser, supplied by Marine7. Both modular barges, with a capacity up to 400t, are transportable anywhere in the world. One barge was designated for the vibro piling operations required to sink the casing to bedrock and the other for the large diameter piling operations required to bore the piles to depth and for socketing the permanent casing.
The project consisted of 20 piles ranging in diameters from 1,120mm to 2,500mm. The piles were fully cased and reinforced with sockets ranging from 3m to 18.5m deep into bedrock giving a fully cased overall length of up to 35m.
Piles constructed from the barge were completed with a new Casagrande B300XP-2 piling rig fitted with an H30 rotary head capable of up to 300kNm of torque and maximum drilling depth of 89.5m with the appropriate Kelly bar.
Quinn Piling is benefiting from the long rotary head stroke and increased working radius of the B300XP-2 rig to construct piles with extended lengths of non-sectional permanent casing. With an overall working weight of 102t, Quinn Piling designed a special working platform and casing guide, placed on the barge, to allow the B300XP-2 to pile over the side of the barge and for the barge to guide the casing during construction.
Sixteen of the piles were constructed from the jack-up barges where only one pile at a time could be completed before moving both barges. This was mostly done at high tide and overnight.
An added complication was that two of the piles needed to be installed at a 1:3 rake (18.3 degrees) and Quinn Piling successfully completed these technically difficult piles with the assistance of stability and work zone calculations provided by Casagrande and an operations area study required as a result of the confined area of the barge.
Complications on the project included the requirement to install two piles at 18.3 degrees
A further complication on the project was the need for two berthing piles with a diameter of 2,500mm and rock socketed to a depth of 15m, being installed on the quayside. A temporary piling platform was constructed on existing piles to allow these piles to be constructed. A second Casagrande B300 piling rig, also owned by Quinn Piling, was used to complete these alongside the offshore piling works completed by the new B300XP-2 rig.
Concreting of the piles was a laborious and time-consuming process as the barge was located offshore and the piles had to be constructed using a concrete hopper chute and tremie pipes.
However, despite all of the difficulties encountered, completion of the project is on target with the new bridge and deck extension due to open in January 2020 for the new Stena Line ferries.
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