A83 Rest and Be Thankful

Published 29th August 2022

Located in Argyll in the west of Scotland, the A83 Trunk Road is a vital social and economic link between the villages of Arrochar and Inveraray. The route passes through mountainous terrain including the pass of the famous ‘Rest and be Thankful’ viewpoint, which has attracted notoriety for being regularly closed by landslides. When the road is closed, it causes many challenges for road users as a diversion of roughly 50 miles is put in place.

These frequent landslides are triggered by high levels of rainfall which lands on steep natural slopes above the road. To mitigate these effects, Transport Scotland has invested in new infrastructure to limit the impact of landslide debris on the road. Waterman was commissioned by Maccaferri Ltd to provide geotechnical design services for the construction of new debris flow barriers.

This phase of work involved the installation of these barriers on the hillside above the road (A83) to intercept debris. The barriers were supplied by Maccaferri Ltd and installed by specialist local contractor Geo-Rope Ltd. The locations of the barriers were determined by the Trunk Road Operating Company BEAR Scotland, under advice from Maccaferri Ltd, and were typically within gullies or across open flanks of hillside assessed as being at risk of instability.

Our geotechnical specialists designed concrete base plinths and their foundations. Additionally, upslope and lateral ground anchors were required in order for Maccaferri to install the flexible debris flow fences. These barriers comprise hinged steel supporting posts from which heavy-duty interceptor panels of steel wire, ring-mesh are suspended. Bracing cables, anchored up-slope, are equipped with brakes to minimise shock loadings on the system during impact by landslide debris. The design of the ground anchors was in accordance with BS 8081 ‘Code of Practice for Ground Anchorages’.

The works were designed to facilitate installation on hillside in remote locations, and due to the use of air lift by helicopter, it was vital for the design to include low weight components.

Client: Maccaferri Ltd