EXPERIMENTAL STUDY ON EFFECT OF BLOCK POROSITY ON OVERTOPPING DISCHARGE

Abstract

 Currently, wave-dissipating blocks of various shapes have been created, but in Japan, the effect of each block on wave overtopping reduction has not yet been evaluated. Some studies have been conducted to represent blocks in a unified manner using the roughness factor γ_f of wave dissipating blocks. Matsushita et al. (2018) and Sawada et al. (2022)have studied γ_f, but data on γ_f is limited and further expansion of data is needed. This study conducted hydraulic model experiments on a steep slope beach using anchor-type blocks to investigate the relationship between block porosity and wave overtopping discharge. A wave overtopping discharge calculation chart was proposed and compared with the results by Yasuda et al. (2022) and Goda's calculation chart (1975). In addition, γ_f was obtained and its relationship with porosity was examined. As a result, no relationship was found between γ_f and porosity. In addition, we proposed to add 7.0 as well as the conventional 4.0 as a boundary of breaker parameter (ξ_{m-1, 0}), and the calculation accuracy was confirmed to be improved.