ABSTRACT
A deep basement was recently constructed in Hawkesbury Sandstone for a property development on Sydney’s North Shore, in Australia, that is located adjacent to critical transport infrastructure. With a depth of over 43m, the excavation is among the deepest basement excavations in Australia. This paper presents the role of Finite Element Method (FEM) as a key design tool in the Observational Method (OM), to make accurate predictions and back-analysis, to overcome geotechnical design challenges, improve construction outcomes, and allow important decisions that may lead to cost savings through an innovative design and construction approach. Applications of smart technologies were use in the instrumentation and monitoring that provided accurate data that was incorporated into the finite element back-analysis.
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.
