Geologists and engineers with a head for heights rock up for National Highways’ M5 survey work
Scaling rock faces high above the ground with motorway traffic roaring below may not be for everyone.
But, as this video footage shows, it’s been all in a day’s work for specialist abseiling engineers carrying out National Highways’ surveys above the M5 Wynhol Viaduct in Somerset, one of the highest and longest rock cuttings on National Highways’ Strategic Road Network.
As part of the 10-year maintenance check on the slopes of the split-level motorway section between junctions 19 and 20, a team of over 20 specialist rope operatives from BAM Ritchies and WSP have been carrying out ultra-safe surveys high above the traffic during the spring.
Travelling motorists may have noticed coned-off lanes, safety fencing and other traffic management on their southbound journeys across the landmark structure but high above them, on the steep rock slopes, teams have been carrying out intensive and lofty geotechnical work.
The Wynhol cuttings were blasted from the hard rock of the Gordano Valley, and the viaduct, constructed soon after as part of the M5 section between the Avonmouth Bridge and East Brent, marks its 50th anniversary this year.
And included in the survey work, at heights of up to 38 metres (125 feet), new, cutting-edge sensors have been installed and existing sensors checked across a mile of the cutting to monitor bolts, anchors and rock strength.
The surveys will inform National Highways whether anchors, bolts and netting will need updating, and during the work more than 800 identification plates were screwed into the rock faces.
As part of the survey, ditches have also been cleared and loose stone removed, along with invasive vegetation from the slopes and crest.
Before work started, more than 45 landowners were consulted, and a state-of-the-art drone survey was carried out to capture the cuttings – at over two miles (3.5km) the longest drone overflight of live motorway in the country.
The drone gathered point cloud and photogrammetric information, which helped the teams to plan access, price the works and record the condition of the rock.
Overnight maintenance work and surveys were also carried out along the northbound median section, some 10 metres below the southbound carriageway, while ongoing ecology surveys are also being carried out across the viaduct and cutting, and ecological teams have also been monitoring and assisting with the geotechnical surveys.
Jon Durnell, Principal Engineer for National Highways’ Geotechnical Asset Management team, said: “We periodically inspect and survey the estate around our roads and structures, the split-level section was built 50 years ago, and rather like your car maintenance, the work represented a 100,000-mile service.
“Given the location of the cutting and the criticality of the M5, a lot of planning and design was undertaken, along with the requisite safety management, and thanks to the collaborative work with BAM Ritchies and WSP, we will now have a lot more information to take us forward for the next 50 years.
“Construction of the Wynhol Cuttings and Viaducts remains a very impressive piece of engineering, with the cuts blasted from the rock in the hillside. It is one of the landmark structures across the Strategic Road Network, and, as with all our structures, we carry out a regular maintenance regime to ensure it stands the test of time.”
BAM Ritchies specialise in ground engineering projects across the UK and overseas, and have carried out work elsewhere for National Highways in the South West along the M4 and A30.
Matt Ewing, BAM Ritchies’ Business Development Manager, said: “Having installed the original mesh, bolts and catch fence back in 2001, it was great to be selected to undertake the second round of 10-yearly inspections, especially after we delivered the last round in 2012.
“The use of rope access techniques, nightshifts, ecologists, detailed planning, and limited traffic management meant the works had minimum impact on the road user and the local ecological environment.
“As principal contractor, our abseiling expertise underpinned a great collaborative effort in meeting National Highways’ needs and providing data to shape their future asset maintenance and pulling on our specialist supply chain in Strainstall and Dywidag we also inspected and tested Dynometers, strain gauges and strand anchors installed in the 1970s when the cutting was created.”
National Highways, the company responsible for England’s motorways and major A-roads, is responsible for nearly 50,000 geotechnical assets on its strategic road network, and the South West team has recently orchestrated work to repair a landslide on the A40 in Gloucestershire, and a collapsed tin mine under the A30 in Cornwall.
For more information on all National Highways’ works in the South West people can follow the company on Twitter at @HighwaysSWEST or visit the National Highways' regional web page.
For the video footage, click on the YouTube link.
Notes to Editors
National Highways is the wholly government-owned company responsible for modernising, maintaining and operating England’s motorways and major A roads.
Real-time traffic information for England’s motorways and major A roads is available via the Traffic England website, local and national radio travel bulletins, electronic road signs and mobile apps. Local Twitter services are also available.
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