Modelling Sydney Opera House Underground Parking Station

The Sydney Opera House Underground Parking Station consists of a doughnut shaped cavern, excavated entirely within Hawkesbury Sandstone beneath the Sydney Royal Botanic Gardens. A model of the excavation was developed and analysed using the Universal Distinct Element Code (UDEC). A brief sensitivity analysis was conducted to determine the sensitivity of the model to the assumed rock mass strength and stiffness parameters. A comparison between the model and monitoring results was made. Finally, conclusions are drawn as to the suitability and usefulness of UDEC in modelling geotechnical structures. The model was found to be extremely sensitive to the adopted rock mass strength and stiffness parameters. This indicates the excavation is approaching the current limits of what can be achieved with respect to underground excavations in Hawkesbury Sandstone. Comparison between predicted and monitored rock mass behaviour, indicated that the UDEC analysis accurately simulated the rock mass behaviour. The analysis highlighted possible failure mechanisms and predicted, to a good degree of accuracy, the orientation and magnitude of likely rock displacements.