Holding rock steady on the M5
Ritchies, the geotechnical division of Nuttall, recently completed stabilisation of a 1.5 kilometre rock cutting on the M5 motorway in North Somerset. Ritchies work included removing more than 40,000 m2 of vegetation and 150 tonnes of bulk rock removal.
After that the 30-metre high rock was provided with netting and rock anchors. Most of the work was carried out by qualified climbers. As the motorway had to remain open mobile rock catch screens were designed. This comprised 15 metre long, six metre high scaffold frames and netting mounted on eight articulated lorry trailers forming a continuous rock fall barrier up to 120 metres long. Other protection measures included blast netting on the face, phased removal and erection of the rock-catch fence and controlled bulk rock removal. The 1.6 million-euro project was completed in ten weeks.