Xbloc and earthquakes - a multi-modal approach to determining revetment performance and repair.

The use of single layer, concrete armour units for coastal edge protection in place of rock is becoming increasingly common. Revetments constructed from these units can provide benefits of a reduced footprint, reduced material usage and transport costs as suitable rock becomes increasingly difficult to source, and reduced construction timeframes. XblocPlus® units have been adopted as the primary armouring for a major shared-path infrastructure project within Te Whanganui-a-Tara, Wellington Harbour. The Ngā Ūranga ki Pito-One Project comprises a 4.5 km shared (pedestrian/cycling) pathway between Ngā Ūranga and Pito-One. The XblocPlus® units are patternplaced interlocking armour concrete units that remain stable at steep slope angles while providing high coastal performance. However, these units have had limited application in seismically active regions. Therefore, the behaviour of the individual armour units and overall revetment during, and following seismic activity was assessed in detail to assess performance and enable development of a post-seismic inspection and repair strategy. The response of a revetment to seismic shaking, particularly the interlocking of the individual XblocPlus® units and interaction with the ground profile below is complex and could not be determined using a single method or model. Therefore, a suite of complementary models was used to assess the behaviour of individual components and combined performance of the revetment asset under the design earthquake events. This paper describes the various physical and numerical models used to determine performance and to inform the design and repair strategy of XblocPlus® revetment. The physics-based model Unreal Engine was calibrated against uni-directional testing on a physical shake table and run for 3D design earthquake timeseries to assess how the individual XblocPlus® units reacted to shaking. Limit equilibrium and time history finite element modelling were carried out to understand how the ground profile supporting the revetment might perform. These results were then used in the 3D physics-based model in Blender to determine the unit response to slope deformation. The XblocPlus® response to shaking and slope deformation was combined to create a post-seismic revetment condition, which in turn was tested by physical modelling in a wave flume against to assess hydraulic stability performance under moderate storm events (i.e., before a repair could be enacted). Following this, an inspection and repair strategy was developed. [ABSTRACT FROM AUTHOR]