CASE HISTORY Ref: UK / CH / RF — Rev: 01, Oct 2018 A82 PULPIT ROCK IMPROVEMENTS LOCH LOMOND, SCOTLAND STABILISATION OF ROCK CUTTING Product: Steelgrid HR 30-Polymer, MacDrain W and Macmat-R Problem - The A82 road winds along one side of Loch Lomond in Scotland. Major re-construction work was needed to improve traffic flow that has been hindered for many years due to a single lane stretch of carriageway on this critical arterial route. The solution to this problem was the construction of a new road lane, however due to the geography of the site the only option was to construct the new lane out over the loch replacing the long-standing traffic light controls which caused lengthy delays. The improvements to the A82 at Pulpit Rock include a new viaduct running parallel with Loch Lomond, widening of the existing carriageway to the north of the viaduct and the introduction of a two-lane carriageway. Solution McLaughlin & Harvey won the design & build contract which Site view before the stabilisation works included earthworks, the formation of new rock cuttings, rock mass stabilisation, construction of the new raised viaduct structure over water and carriageway construction and commissioning over a 400m length of the shores of Loch Lomond. The formation of the new rock cut and stabilisation of the parent rock mass was considered one of the most challenging aspects of the project. The original engineering design included the augmentation of the rock mass stability by the installation of rock anchorages across the face of the slope. The design also required the installation of a stabilisation netting system to support any surfacial instabilities in the finished slope profile - a high strength and high stiffness mesh was required. Steelgrid HR system was chosen due to its high strength and high stiffness plus its compatibility with the anchor pattern and ease of connectivity to the slope surfacing solution. Due to the client requirement for a long design life combined with the exposed lochside location of the site and the extensive use of de-icing salts on the A82 trunk road, the polymer coated version of Steelgrid HR30 mesh was chosen as the facing system for the slopes. Faults in rock with associated fault gouge and the potential for increased permeability and water flow were present. Accordingly, MacDrain was laid over the existing rock prior the installation of the Steelgrid HR-Polymer mesh. The use of drainage geocomposites allow water seepage issues to be overcome without the need for extensive engineering works. Since the site is situated within the ‘Loch Lomond and the Trossachs National Park’ and the ‘Loch Lomond National Scenic Area’ blending the visual appearance of the Client: TRANSPORT SCOTLAND Main contractor: MCLAUGHLIN & HARVEY Designer: TONY GEE (ESHER OFFICE) Products used: Vegetative soil wrapped on Macmat-R. STEELGRID HR PVC, MACMAT-R & MACDRAIN Date of construction SPRING 2015 geotechnical solution within the environment was a priority. To allow the establishment of vegetation on the rock cut, pre- seeded top soil mix was wrapped in a specially folded containing layer of reinforced geocomposite mesh, Macmat-R. The Macmat-R was then secured to the high resistance Steelgrid HR 30-P stabilisation netting system. The finished solution provides a uniform vegetated face to stabilised rock cuttings at the site that blends in well in this area outstanding natural beauty. Macdrain was placed over the existing exposed rock View of the rock cutting slope at initial stages. Works completed in 2015 Aeriel View of the works View of the vegetated rock in 2016 Vegetated slope—Autumn 2018 Vegetated slope—Autumn 2018 enforce Copyright. willrights Maccaferri © Maccaferri All reserved. Ltd. Maccaferri Ltd: Specialist areas: Building 168, Harwell Campus, Didcot, OX11 0QT Sales: E: [email protected] T: (+44) 1865 770555 Technical: E: [email protected] Rep of Ireland: Construction: E: [email protected] T: (+353) 18851662 www.geostrong.net www.maccaferri.com/uk .