The Gibraltar Tunnels

The Gibraltar Tunnels are twin road tunnels carrying the A40 trunk road near Monmouth. The project involved targeted structural maintenance to the tunnel linings using dry sprayed concrete to address deterioration and extend the asset’s service life

The tunnels are adjacent to the River Monnown and this meant close attention was required to ensure all arisings from the works were carefully controlled, especially the water. Approximately 20,000L of water was used and captured daily during the Hydro demolition works. Due to the close proximity of the defects, the works in each bore were planned in 3 phases in order to reduce the area of soffit opened up at any one time in a given area. This meant the whole process was repeated end to end, in each bore 3 times with the tanking to the road surface reinstated each time.

• Restoration of damaged tunnel linings to a
  safe and durable condition
• Improved long-term resilience against
  water ingress and carbonation
• Extended service life of the tunnel asset
  with reduced future maintenance demand
• Minimal disruption to strategic traffic flow
  through phased working
• Enhanced inspection records and updated
  condition assessment data for future asset
  management