FUNDAMENTAL STUDY ON THE INFLUENCE OF POROSITY ON ROUGHNESS FACTOR OF MODELED WAVE DISSIPATING WORKS

Abstract

 Various structures using wave-dissipating blocks have been used for coastal protection and disaster prevention. The roughness factor γ_f can be used to evaluate the amount of wave overtopping of wave-dissipating blocks, enabling highly accurate estimation according to the type of blocks. γ_f is a value specific to the wave-dissipating blocks and is considered to be determined by the porosity and the shape of the dissipating blocks. However, basic characteristics such as the effect of porosity and the shape of the wave-dissipating blocks on γ_f have not been investigated sufficiently. In this study, we aimed to clarify the effect of porosity, which is one of the basic factors, on γ_f . Hydraulic model experiments and numerical calculations using a porous model were conducted by changing the porosity without changing the shape of the wave-dissipating blocks. Both experimental and numerical results showed that γ_f reached a minimum around the porosity of 70%.