Stabilising Arley Tunnel
The Midland Railway opened Arley Tunnel in 1864 to connect Birmingham to Leicester in England’s Midlands region. The tunnel is built on the highest section along the route between Arley and Stockingford. A combination of the local geology and previous coal mining in the area can trigger landslides and rockfalls near the tunnel. To rectify the situation, Network Rail implemented a multibillion-pound railway upgrade plan, including stabilising work to ensure the tunnel’s structural integrity.
CAN Geotechnical, an RSK company, worked with contractor J. Murphy & Sons throughout the £6-million project, from 2015 to 2019. Initially, our specialists advised the contractor on the project’s design and methodology while Network Rail was finalising the scheme’s remit. Once contracted for on-site work, we installed more than 2200 soil nails (6 m), several 3-m rock bolts and a mesh facing system that stabilised the cutting slopes. Because the cutting area was 20 m deep and 230 m long, we attached 8500 m2 of high-tensile mesh to both sides.
Minimising disruption to the line throughout the project was paramount, so CAN used its technical ability and innovative in-house equipment to work during the day while the line remained active. We installed permanent soil nails as anchor points for our bespoke temporary catch fence; the simple, angled coupler system enabled our engineer to tailor the angle of the fence to the specific geometry of the site, thereby ensuring the highest level of protection to trains running through the cutting. The fence’s design negated the need to drill extra anchor points, which further enhanced on-site safety.
The construction programme was developed to focus on completing possession-dependent work in each of the 10 site subsections, thereby releasing each area for safe daytime working. Using up to six drill rigs simultaneously maximised drilling output, and we completed the drilling works according to schedule. Labour was resourced accordingly, so each support task, such as testing and installing the netting facing system, ran concurrently to drilling. CAN Geotechnical completed its on-site work at the end of August 2019.