Large-scale experiments on tsunami-induced pressure on a vertical tide wall

• Large-scale experiments on the pressure on a wall due to tsunami were conducted.
• We investigated characteristics of the pressure for three different phases.
• A modified solution to predict the pressure in the bore impact phase was proposed.
• Collapse of water column increases pressure in the initial reflection phase.
• In the quasi-steady-state phase, pressures profile hydrostatically.

Large-scale experiments on the pressure exerted on a tide wall due to the impact, reflection, and overflow of tsunami inundation flow were carried out to investigate the characteristics of the pressure and the flow in front of the tide wall in the bore impact, initial reflection, and quasi-steady-state phases. The Central Research Institute of Electric Power Industry (CRIEPI)'s Large-scale Tsunami Physical Simulator, in which large and long tsunami inundation flows can be reproduced, was used in the experiments. In the impact phase, two types of short-duration pressures with durations in the ranges of 10− 3 to 10− 2 s and 10− 1 to 1 s were observed. The latter pressure can be partially predicted by Cumberbatch's theory (1960). For cases of tsunami bore with high impact speeds, the theory obviously overestimates the impact force. For cases of tsunami bore with low impact speeds, the forces predicted by the theory agreed reasonably well only with the forces measured just after the bore impact. By contrast, the forces predicted by the modified solution of the theory agreed well with the measured forces for these cases. In the initial reflection phase, pressure greater than the hydrostatic pressure at the depth of the incident bore was exerted at heights above the depth of the bore. The most likely cause of this is the collapse of the water column. In the quasi-steady-state phase, the pressures were almost equal to the hydrostatic pressure upstream of the wall. The pressure and the flow reached the quasi-steady state within a few seconds after the bore impacted the wall.