Pore Water Pressure Response during Tsunami Loading

Abstract

Tsunamis induce excess pore water pressure gradients in coastal sediment beds. The excess pore water pressure gradient induced during tsunami loading along with the shear stress caused by the tsunami flow can cause significant sediment instability and enhanced scour. Herein, a coupled seepage-deformation model is implemented to estimate the pore water pressure response in the soil during tsunami loading. First, the mechanism of sediment instability during tsunami loading and the delay in the pore water pressure response with depth are investigated. Second, the effect of tsunami height, duration, and impermeable layer depth on the sediment instability and the depth of instability are investigated. Finally, the soil liquefaction potential is evaluated using the effective stress based definition of liquefaction and pressure head gradient viewpoint. The results show that momentary liquefaction with a high excess pore water pressure gradient can occur during a tsunami. The numerical experimentation shows that tsunami properties and impermeable layer depth can significantly affect the excess pore water pressure gradient and the depth of instability during tsunami loading.