Effect of wave height on seismic fragility of subsea tunnels in sandy seabed

The combined of earthquakes and waves cause significant challenges to the subsea shield tunnels in liquefiable seabed. Present seismic fragility analyses of the subsea tunnels have largely overlooked the coupling effect of wave action and seabed liquefaction. This study addresses this gap by employing a numerical model that integrates Biot theory with a modified generalized plasticity model. The effect of the wave height on the tunnel fragility is investigated through the incremental dynamic analysis, which adopts 18 seismic records scaled to 10 intensity levels. The damage probability of tunnels is governed by the interplay between seismic intensity and wave height. Particularly, a rise in wave height leads to greater liquefaction depth and higher bending moment of tunnels, particularly elevating the damage probability of tunnels under high seismic intensity conditions. The finding highlights the combined influence of wave action and seabed liquefaction on seismic behavior of the tunnel – seabed system and provide novel insights for improving the resilience of subsea tunnels in liquefiable seabed prone to multi-hazard interactions.