The scope of the work performed by Atteris was to verify that the mattresses proposed for use as pre-lay span supports at various locations along the installation route of the Wheatstone, including the Roller/Skate crossing were stable for 100-year Return Period (RP) cyclonic conditions. Each mattress configuration was assessed for global lateral and vertical stability, as well as edge lift stability.
Given the limitations on allowable installation loads, it was recommended to install the mattresses individually.
Misalignment of stacked up mattresses was found to introduce the potential of increased hydrodynamic lift force, escalating the risk of edge lift. On that basis, Atteris recommended to assess the risk of mattress misalignment, which if significant, would require further investigation into the stability of the stacked mattress to ensure the design requirements were met.
