Tunnelling finishes on major UK gas supply project

After completing an incredible first in the UK – digging a tunnel 5km from Goxhill in North Lincolnshire to Paull on the north bank of the Humber river - National Grid and project partners Skanska, PORR and AHak have bid farewell to ‘Mary’, the 160m long tunnel boring machine that completed the job.
Tunnelling finishes on major UK gas supply project Tunnelling finishes on major UK gas supply project Tunnelling finishes on major UK gas supply project Tunnelling finishes on major UK gas supply project Tunnelling finishes on major UK gas supply project

Mary the TBM, completing the 5km journey from Goxhill on the south side of the River Humber to the specially constructed shaft at Paull on the north bank

Duncan Moore

Editor

Duncan Moore

Following the breakthrough at Paull on 10 September, the TBM was dismantled and lifted to the surface ready to be shipped back to Germany to be fully refurbished ready for her next tunnelling challenge.

For the last 18 months, she has been steadily making her way from Goxhill on the south side of the river to Paull on the north bank, constructing a tunnel nearly 5km long and 3.65m in diameter, ready to carry a vital pipeline which can provide up to a quarter of Britain's gas supplies.

During Mary's journey under the Humber, approximately 160,000t of material were excavated - 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.

"Mary has completed a fantastic feat of engineering and it's great to see her on her way 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 River 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 epic task of carefully pushing eight 610m long and 850t 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.

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