About This Project
The reconstruction of Farnworth Tunnel was an important stepping stone in creating an electrified railway, and from 2016 better trains now operate between Manchester and Preston providing more capacity on the line.
Network Rail took the larger of the Farnworth tunnels and made it bigger, putting both tracks and the electrical equipment through that tunnel. This resulted in Farnworth station and its platform being shifted to the side slightly to meet the new track. The line speed was increased to 100 miles an hour, the track and and four bridges were lowered, and a pedestrian level crossing was closed and replaced with a footbridge.
The project was a complex and challenging engineering project. The first stage was to install a concrete liner to the smaller down tunnel so that a passenger service was maintained, and this also secured the tunnel while the works were undertaken. Then a specialist piece of tunnelling equipment bore out almost 300 metres of the existing tunnel and created a new larger tunnel capable of accommodating both the tracks.
A comprehensive monitoring programme was required to validate design assumptions, confirm anticipated ground/structure movement and to ensure workforce and train safety.
The objectives of the monitoring programme were as follows:
- To monitor movements in the SCL strengthened Down Tunnel to ensure railway operational standards are not compromised
- To automatically monitor any movements in the existing brickwork lining of the Down Tunnel as a result of the partial removal of the brickwork
- To monitor track movements on the bi-directional Down line using Automatic Total Stations
- To provide an automated alarm in the event of the movements exceeding the trigger values settled
- To report daily to the construction management using diagrams and visualisations generated with the Kronos monitoring system
- Monitoring movement of the A666 as a result of the New Tunnel construction
- Monitoring any movement of the existing masonry portal walls during the temporary works and launch/removal of the tunnelling shield
- To monitor the Cemetery Road Shed, structure in the zone of influence
All monitoring works were carried out and finished in time and to the full satisfaction of our client the Murphy Group and Network Rail.
Murphy Group for Network Rail