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The Gift Of The Gabion

Trains are set to start running this month on the longest domestic passenger railway to be built in the UK for a century. GE finds out how retaining wall technology has been used on the Airdrie to Bathgate line.

This month the first train will run on the Airdrie to Bathgate line in more than 50 years.

Network Rail has invested £300M in widening the archaic route which runs through the small communities between Edinburgh and Glasgow.

Reopening the route will provide a vital connection to Scotland’s two biggest cities for communities in North Lanarkshire and West Lothian.

According to Network Rail, at 24km the rail line is the longest domestic passenger railway to include new stations to be built in Britain in over a century.

Three new stations will be built in total, at Armadale, Blackridge and Caldercruix and two stations, Bathgate and Drumgelloch, will be relocated.

Once work is complete, the line will be double-tracked and electrified from Edinburgh to Glasgow and passengers will be able to travel continuously through to Helensburgh on the Firth of Clyde.

To strengthen cuttings and embankments along the old route, gabion technology has been used.

Gabions are rectangular box units, typically 2m x 1m x 1m, made from a double twist mesh of soft annealed, heavily galvanised wire.

When filled with stone they become large, flexible building blocks from which a broad range of mass gravity retaining structures can be built.

The main advantages of gabions are their strength and flexibility.

Rail_Link

Their wire construction can easily tolerate differential settlement.

Hydrostatic pressure does not build up behind the units because of their permeable nature.

The ability to combine drainage and retention functions make them well suited for slope stabilisation.

Contractors Bam Nuttall and Carillion used gabions manufactured by Maccaferri as retaining walls where the old single track line has been widened to accommodate twin tracks as well as with maintenance access walkways and drainage/cabling runs.

At the western section, between Airdrie and Drumgelloch stations, the old single track line threaded its way through heavily built-up residential and industrial areas.

Here, Bam Nuttall, which is responsible for building the new station at Bathgate and a range of earthworks across the route, has used more than 1,800m2 of pre-filled gabions to create retaining walls up to 4m high around signal gantries next to the line.

“Access to the work-site was particularly tight here so we decided to use gabions which had been pre-filled with stone, then craned them into position,” says Bam Nuttall site agent Chris Neuwirth.

“We only had an eight-week window within a 15-week programme so speed of installation was a deciding factor. Pre-filled gabions gave us the flexibility we needed,” adds Neuwirth.

Maccaferri_Gabions_A_to_B_Caldercruix_2

Gabions were also used to support a deep rock cutting further east at Raisehill.

The walls, 25m long on the north side and 85m long on the south side of the line, also allowed the relocation of a small factory-farm next to the track.

Contractor Carillion is building the three new stations across the route.

At Caldercruix, it built gabion walls that are 72m long and 4m high on the north side and 10m long, 2m high on the south side to allow widening of the rail corridor and the construction of a new station complex.

To speed progress Carillion brought in Maccaferri’s construction arm to install, as well as supply, the gabions.

Installation of the two walls took only six weeks.

Work began on the site in June 2008, and now, just 18 months later, trains are set to run again throughout the communities of central-Scotland.

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