A 3D Ground Surface Model of Mount Ousley Road: Modelling the Interface of Quaternary and Bedrock Material Underneath a Major Highway Mountain Pass

The geology that underlies highway mountain passes is a significant factor that should be considered in the construction, maintenance, and monitoring schedule of infrastructure that exists within these areas. This thesis focuses on 3D mapping of the geology beneath Mount Ousley Road, a major road corridor that links Wollongong and Sydney. This project paid particular emphasis on mapping the boundary between unconsolidated Quaternary alluvium and colluvium, and underlying geological units. The 3D model was constructed within the ArcGIS Pro and IPM-MOVE software packages. The 3D model was developed using existing geological maps, and constructing geological cross-sections that incorporated borehole logs that were digitised from hardcopy logs supplied by Transport for New South Wales (TfNSW). The model allowed for the construction of a 3D surface of the interface between Quaternary material and bedrock. Preliminary mapping was also undertaken regarding the surrounding geological units, but further data and modelling is necessary in this regard. Additionally, the movement of the Quaternary colluvium was also investigated via the use of inclinometer data supplied by TfNSW. These three aspects of the model allow an investigation into the relationship between underlying structural geology and the movement of Quaternary colluvium downslope, where it was found that the geometry of the underlying interface has an impact on the movement of the material in the study area.