Ground Response Due To Deep Excavations In Sydney Sandstone

A deep basement was recently constructed in Hawkesbury Sandstone for a property development on Sydney’s North Shore located adjacent to critical transport infrastructure. With a depth of over 43m, the excavation is among the deepest basement excavations in the world. This paper presents the geotechnical design challenges, construction outcomes, use of the Observational Method (OM) on the excavation, discusses cost savings through innovative construction and design, and presents applications of smart technologies to instrumentation and monitoring.

When unusual displacement was observed adjacent to the transport corridor due to structural uncertainties and construction activities, the OM and verification process provided a flexible framework within which to reassess ongoing movements and effects on adjacent infrastructure to ensure construction could proceed safely. The case history demonstrates the benefit of adopting the OM for excavations to achieve savings in time and cost, and to react to unexpected movements during construction.