Industry-wide need for a standardised approach to condition monitoring and maintenance of rock netting was identified as priority by the UK’s leading infrastructure organisations at a meeting last week.
The Geotechnical Asset Owners Forum (GAOF) identified a need for advice for longer term monitoring, assessment and maintenance strategies during the meeting in Northern Ireland.
Practical challenges of design and installing rock netting systems were highlighted by a visit to various sites on the main Antrim A2 coast road organised by the Northern Ireland Roads Services, including the recently completed netting work at Garron Point where a rock fall in 2009 closed the road.
The site visit was followed by a roundtable discussion of current practice and the challenges this presents to on-going asset management.
Network Rail route asset manager – civil engineering (Kent) Derek Butcher outlined the scale of the issue by telling the group that in his area Kent has secured £14.9M funding to reduce the risk from rock cuttings. “This funding will allow us to address almost 15km of the network at risk from rock slope failures but addition of rock nettings will add to the maintenance demands,” he said.
Butcher’s colleague senior asset engineer Clare Brint added that Network Rail currently uses the Rock Slope Hazard Index to assess netted slopes but that it was never intended as an inspection tool.
According to the group, which also includes representatives from the Highways Agency, Transport Scotland, Transport Wales, ADEPT and the Canal & Rivers Trust, there is some good guidance available covering the design and initial remediation of rock netting systems. However there is a distinct gap in advice when it comes to assessing the effectiveness of aging bolts, anchors, netting and cables.
GAOF members have agreed to work together to develop a standard for monitoring and maintenance and a CIRIA guide on the issue could result from the agreement if funding from other stakeholders in the sector can be secured.