Engineering geological models in remote and difficult access terrain: A case study from Bogong High Plains Road

A significant landslide closed access to Falls Creek via Bogong High Plains Rd in October 2022. An investigation into the potential to open a temporary four-wheel-drive access to Falls Creek via steep terrain adjacent to Lake Guy was completed. The site had difficult access, remote location and limited time for investigation.

For a small project area there was significant variation in slope performance and geology, including colluvium and residual soils overlying exposed granodiorite and metamorphic bedrock. The study considered the rich history of engineering geological studies associated with past hydropower projects to establish broad structural controls on the topography before developing the local engineering geological model. Traditional desktop, geomorphological and field mapping techniques were adopted to characterise the slopes and assign appropriate domains. The domains then directly informed the assessment of landslide hazards and remedial design advice. Landslide hazards were assessed using the Department of Transport and Planning “Roadside Geotechnical Hazard Risk Management” guideline. Domains were validated with a series of test nails/bolts as mobilisation of slope stabilising contractors was imminent.

The case study highlights that meaningful, cost-effective engineering models can be developed without traditional intrusive site investigation methods and that engineering geological models should underpin landslide assessment and remediation.