ANALYTICAL STUDY ON THE IMPACT OF TSUNAMI DENSITY ON THE WAVE FORCE ACTING ON SEAWALLS

Abstract

 The "black tsunami" observed during the Great East Japan Earthquake raised concerns that the wave force exerted on structures could increase more than the density increase rate. In this study, we refered to previous hydraulic experiments and used the numerical analysis model developed by Yoneyama et al. to replicate the black tsunami and examine the impact of tsunami density and viscosity on the wave force acting on vertical walls. After verifying the model's validity through previous experiments and empirical formulas, various conditions were analyzed.

 The results confirmed that with an increase in density (1.5 times, 2.0 times), the wave force increase rate ranged from 0.85 to 1.25 times the density increase rate. Additionally, in cases where the wave force increase rate exceeded the density increase rate, the water depth and flow velocity before the flow impacted the vertical wall increased. Conversely, with an increase in viscosity (10 times), the range of the wave force increase rate narrowed to 0.9 to 1.2 times, and the effect of increasing water depth and flow velocity tended to decrease. These findings offer valuable insights for understanding the relationship between wave force and the density and viscosity of black tsunamis, contributing to improved disaster prevention and structural design.