29.10.15
Major breakthrough as Farnworth Tunnel re-boring comes to an end
North west electrification works have hit a major milestone as Britain’s biggest active tunnel boring machine (TBM), the 9m-wide Fillie, broke through Farnworth Tunnel on Sunday (25 October).
Farnworth Tunnel features two single-line tunnels built in the 1800s that were not large enough to deliver the electrification project. As a result, the larger of the two tunnels had to be filled in with 7,500m³ of foam concrete and then re-bored, making it big enough for both sets of railway lines and the overhead equipment.
The adjacent down-tunnel, which runs south-east, was strengthened to allow some train services to continue to operate during the project.
Contractors J Murphy & Sons celebrated the major breakthrough, with its project manager on the scheme, Mick Boyle, commenting: “Breaking through with the TBM yesterday is a big step to ensuring that the tunnel is secured for many decades of providing a more efficient railway for Network Rail and passengers.
“This has been an exciting project to work on and demonstrates the skills of our team who have worked very hard to ensure that we have reached this milestone.”
Fillie after completing Farnworth Tunnel
Network Rail told RTM in a statement that full details of the reopening of the two-track railway near Bolton will be release as soon as possible.
And its route delivery director, Nick Spall, said: “Farnworth Tunnel is an extremely complex and challenging project in our railway upgrade plan. Breaking through to complete the tunnel is a key milestone for the project. There is still a lot of work to do, and our priority is to get passenger services returned to normal as soon as possible on this key passenger route.
“This will require a short closure of the railway and we are carefully planning this with the train operators to cause the least amount of disruption possible.”
RTM had visited the tunnel in August where Spall discussed how the major work was helping deliver further electrification in the region, shortly after Fillie had started re-boring the 276m railway tunnel.
In September, Martin Frobisher, route managing director at Network Rail, told RTM that Farnworth Tunnel construction work would be delayed possibly until December after engineers hit an area of running sand on 14 August. This slowed down progress and created big voids, the largest of which needed filling with around 35 tonnes of grout.
Engineers were then tasked with pumping resin into the ground to firm it up before Fillie bored through it.
As a result of unexpected ground conditions, work could not be completed by the initial deadline of 5 October.