“The A465 Heads of the Valleys Road runs across the northern edge of industrial South Wales, providing an east-west connection between west and east Wales,” the article begins. “The Welsh Government announced an ambitious plan to improve this main arterial trunk road, which in turn is critical in the social and economic regeneration of the area, by upgrading the road to a full dual carriageway along its entire length. For ease of delivery, Welsh Government have split the projects into a number of sections; section 1 (Abergavenny to Gilwern), section 2 (Gilwern and Brynmawr), section 3 (Brynmawr to Tredegar), section 4 (Tredegar to Dowlais), Section 5 (Dowlais to A470) and Section 6 (the A470 junction to Hirwaun).”
In 2014, CAN conducted initial slope stabilisation works in one area of section 2, a three-lane carriageway that runs through hilly landscape on the edge of the Brecon Beacons National Park. Improving the road through this undulating terrain presented several challenges, including demanding “extensive earthworks and the removal of well over 1.2 million tonnes of material to facilitate the creation of the many cuttings and embankments along the route. In addition, many sections of the road required widening and it has therefore been necessary to cut into the adjacent hillside, resulting in the significant steepening of the road boundary, which brought about intrinsic destabilisation.” CAN’s brief was to stabilise these steepened slopes.
Soil nail drilling
From the initial work in 2014, CAN has successfully won and delivered 41 individual stabilisation work packages along the route and is continuously on-site. The programme of work has included temporary and permanent stability solutions, including catch fences and rockfall netting while the work was ongoing, and a mixture of soil nails, rock bolts, sprayed concrete, wire-basket gabions, reno mattress, erosion matting and netting permanently deployed across the route. The project has seen the installation of 11,000 soil nails that required an estimated 45 miles of borehole drilling, the mobilisation of nine different drill rigs, and the installation of 36,000m2 of netting to date.
CAN’s work will be ongoing until late 2019, when project completion of section 2 will be finalised. You can read the case study in full on the Construction Update website.