Tunnel helps the Gateway project
ANOTHER milestone has been reached on the Mersey Gateway project with the use of one more special engineering solution to complete a vital rail bridge in Widnes.
The Freight Line Bridge has been specially designed as an opti-cadre portal, also known as a pre-cast concrete tunnel.
The design was specially chosen for speed of build, short construction time and minimal disruption to the rail infrastructure, whil providing a solution allowing traffic to pass over the top once completed.
At 99.4m long, 14.5m wide and 6m high, the huge structure has taken a high degree of engineering to con- struct and will be installed over the Garston to Timperley line which is only used for freight trains.
Merseylink general manager Hugh O’Connor said the reason such a unique structure was specified is due to very poor ground conditions at this part of the site.
He said: “To install the bridge a steel sheet pile wall consisting of a total of 176 driven sheet piles was installed before excavating and then constructing a foundation pile cap.
“Throughout the work the railway track was constantly surveyed using specialist fixed prisms, which allowed the position of the track to be carefully monitored.
“Deep soil mixing was also conducted on both sides of the railway to make sure the required ground settlement at the site was achieved. ●
“After mixing was complete, embankments were built either side of the railway track before the precast concrete portal was installed.”
It is made of 112 base walls and 56 roof units, with the biggest unit weighing in at 51 tonnes.
A Mersey Gateway spokesman said the Freight Line Bridge is a ‘fine example of modern engineering techniques’ and its completion follows a variety of other major project milestones.
Last month the huge North Approach Viaduct structure was completed. It contains enough concrete to fill seven Olympic-sized swimming pools.