A THEORETICAL ANALYSIS OF OCCURRENCE OF HYDRAULIC JUMP BY DOUBLE EMBANKMENT SYSTEM

Abstract

 After the Great East Japan tsunami, against a Level 2 tsunamis, the goal of the coastal defence is not ‘disaster prevention’ but ‘disaster mitigation’ by compound defence system. As a compound defence system, double embankment structure was previously investigated by experiment and the flow structure in between two embankments was demonstrated to affect the reduction of tsunami energy. Especially, the flow structure which hydraulic jump occurs in between two embankments is suitable because the energy reduction is high and the oscillation of water level at the top of second embankment is not observed. Therefore, in this study, a theoretical equation to estimate the critical occurrence of hydraulic jump by double embankment system was proposed. By comparing the theoretical equation with the experimental data in a previous study, the applicability of the equation was validated. In addition, the friction loss equation was suggested not to be applicable for a run-up flow.