‘Mary’ the 4m diameter Herrenknecht TBM boring the UK’s 5km long, 3.65m diameter River Humber replacement gas pipeline tunnel broke through on Tuesday September 12th. The breakthrough, into the specially constructed shaft at Paull on the north bank of the river, marks the end of her 18-month journey, at depths up to 35m, from Goxhill on the south side.
The £100M tunnel has been constructed by a joint venture made up of Skanska, PORR Bau GmbH and A. Hak, and features a pre-cast lining with each ring formed of six segments.
During her journey under the Humber, ‘Mary’, has excavated approximately 160,000 tonnes of material – mostly chalk, which has been carefully transported back to the surface, graded and re-processed at the Goxhill slurry treatment plant. The excavated material is being used to help restore a former quarry nearby.
Steve Ellison, Lead Project Manager, Capital Delivery, for National Grid, said: “Completing the tunnel beneath the Humber is a major milestone for the project team and our project partners. It’s the first time a tunnel has been constructed beneath the River Humber and a fantastic achievement for everyone involved.
“Over the next few weeks we’ll be dismantling the tunnel boring machine and lifting her out of the ground in sections, ready to be transported back to Germany, where as much as possible will be refurbished and renewed to get her ready for her next tunnelling job.
“The next steps for us here under the Humber involve clearing the pipes, cables and ancillary equipment that has been servicing the tunnel boring machine and preparing for the world record breaking pipeline installation early next year.”
In Spring 2020, two hydraulic thrust machines will start the task of pushing eight 610m long and 850 tonne sections of pipe on rollers into the new tunnel from the Goxhill side. The pipes will be pushed at about one metre per minute into the tunnel which will have been flooded with water to aid installation.
When one pipe section has been installed, the next will be moved into position, welded to the one in front, and the push will continue until all 5km of pipeline is installed beneath the river. When complete it will be the longest hydraulically inserted pipe in the world.