This paper presents two case studies where detailed site specific engineering geological assessment during construction justified major changes to the approved design of road infrastructure elements to suit actual site conditions which resulted in a better engineering outcome and substantial cost savings. The road project was the Hunter Expressway, located in the Hunter Valley, some 120 km north of Sydney, which is a 40 km long four-lane dual carriageway motorway currently at the final stage of construction. Two locations (Bridge Viaduct 3 and Retaining Wall—RW18) were selected as case studies because the detailed construction-phase mapping work provided a refinement to the geological models that enabled the design of key elements to be changed or modified. This paper will present the detail of these two case studies and demonstrate the value of detailed site specific engineering geological assessment during construction in achieving better engineering outcomes.
