Rock cut on the A5 at Glyn Bends, North Wales, UK
This paper discusses the challenges involved in the upgrading of the A5 London to Holyhead road through Glyn Bends, an area of natural beauty adjacent to the Snowdonia National Park in North Wales. At the location where it passed through a steep gorge in the Ordovician metasiltstones, part of the original road was supported on 200 year old, 10 m high retaining walls. The metasiltstones contain some low strength bands of volcanic ash, on which a planar failure had taken place prior to the construction of the original road. This paper discusses the up-grading of this part of the A5, which involved a 550 m long, 25 m deep cutting and an 18 m high embankment. This work was designed to minimise the visual impact in this environmentally sensitive area, while limiting the interruption to traffic on a significant trunk road.