Numerical Investigation on the Behaviour of Floodways Under Extreme Flood Events

Floodways are infrastructure utilised in road design to allow safe vehicle passage across waterways. They are also a practical solution for state and local governments to implement in roads which have low traffic volumes as flood events are typically infrequent and of a short duration. Recent extreme flood events in Queensland have revealed that floodways frequently sustain damage due to the presence of high debris and impact loadings. Currently Australian design guidelines consider hydraulic principles only and do not consider the influence of structural loadings acting on floodways in frequently submerged states. Comprehensive analysis of their failure mechanisms has exposed deficiencies demanding the need to investigate their structural adequacy. This research through a detailed parametric analysis using 3D finite element modeling identifies the current design factors and load combinations which contribute to floodway vulnerability. Strength capacity design charts based on the worst case loading conditions are then assembled for different commonly encountered soil types, flow depths and flow velocities. Referencing these charts enables a user to accurately design structural elements in reference to AS3600. An integrated design process has also been developed to incorporate this simplified structural analysis method with the current procedures outlined in Australian design guidelines. It is anticipated that this research will present a holistic approach for the future construction of floodways in Australia, which will reduce maintenance and periods of unserviceability in the wake of an extreme flood event