At a low crown caisson seawall with a large-size wave overtopping drainage, the pick-up of blocks on a caisson mound is one of the important issues in the design of seawall. Therefore, in this study, a simulation by the DEM-MPS hybrid model is carried out. In this model, fluid is calculated based on the MPS method and blocks are tracked by the DEM. In a calculated result, blocks around the top of mound slope are picked up. This fact agrees with the hydraulic experiment.

INTRODUCTION

One of the significant design issues of a low crown caisson seawall with a large-size wave overtopping drainage is the pick-up of blocks on a caisson mound due to high wave impact. In the process of wave overtopping in this kind of seawall section, a part of water which flows over the caisson falls down in front of the caisson. The investigation of a velocity field around armor blocks is needed to examine a mechanism of the pick-up of blocks, however, it is difficult to measure a velocity field in a hydraulic experiment due to bubbles generated by falling water in front of the caisson, and the current meter can be damaged by picked-up blocks. Hence, the application of the numerical analysis must be key of the examination of the pick-up of blocks. Gotoh et al.(2007 and 2008) carried out the simulation of wave overtopping in this kind of seawall by the particle method and examined the reproducibility of this numerical model. Moreover, the pick-up of armor blocks was predicted on the basis of the CERC formula with using simulation results by the particle method. However, for more accurate prediction, it is unavoidable to track blocks. Therefore, in this study, the simulation of the pick-up of armor block is executed by using the particle method which is suitable for treatment of a moving object.

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