MHB Consultants was appointed by QTS Group on behalf of Network Rail to provide geotechnical design services for a soil cutting on the Scottish Central Main line, located between Bridge of Allan and Dunblane. The Down side cutting, reaching heights of between 10 and 13m, had a documented history of shallow slope failures with previous incidents in 2011 and 2012 resulting in material reaching the track on an electrified twin-track line operating at 70mph.
The works covered three discrete sections of the cutting spanning approximately 1.4km. Each section presented its own challenges — from dilapidated crest drainage and oversteep slopes at the lower mileage end, to landowner access towards Dunblane. Geophysics survey was carried out to understand ground conditions across the sites with limited access.
Slope stability analysis was carried out using GeoStudio’s Slope/W software, with design undertaken in accordance with Eurocode 7 and BS8006. Geobrugg Tecco Green netting and self-drilling soil nails were proposed across Sites 2 and 3, covering a combined area of approximately 4,600m². Crest drainage maintenance was proposed across all three sites, with CCTV survey and mechanical raking of the French drain at Site 3, and slope monitoring implemented towards the high mileage end where ground movement remained a concern.
