BAM Ritchies

Case Study: M5 Wynhol Viaduct Rock Face Stabilisation

Client: Highways Agency

Engineer: W S Atkins

Main Contractor: BAM Nuttall Ltd

Location: Bristol

Date: 2001

The stabilisation of a 1.5km length of rock cutting on the busy M5 motorway in North Somerset called for an integrated team effort from the client, engineer and contractor.

Working with the Highways Agency and Engineer WS Atkins Ltd, BAM Nuttall’s local civil engineering division undertook the traffic management operations while BAM Ritchies undertook the main stabilisation works on the 30m high slope.

The contract employed around 50 people at its peak and was completed in 10 weeks, 2 weeks ahead of programme. Principal elements of work included:

  • 47,500 m2 of vegetation removal
  • 5,500 m2 of rock scaling
  • Approximately 150 tonnes of bulk rock removal
  • Over 6,500 m2 of rock meshing
  • Numerous areas of new dentition, repointing and buttressing
  • 250 face pins and rock bolts
  • 1.5 kms of rock catch fence

The majority of the work was undertaken using rope access techniques with up to 20 IRATA qualified climbers being employed at peak times. Rock bolts were generally installed by use of high reach cherry pickers mounted with rock drills.

A key element of our solution was the site specific traffic protection measures on the adjacent M5. Most significantly, these included the design and construction of a mobile rock catch screen. The screen comprised 15m long, 6m high scaffold frames and netting mounted on 8 articulated lorry trailers providing a continuous rock fall barrier up to 120m long. Other measures included blast netting on the face, phased removal/erection of the rockcatch fence and individual procedures for controlled bulk rock removal.

Both early completion and the removal of lane closures over half term weekends were key benefits to the client in their quest to minimise disruption to the travelling public throughout the course of the works.