Development of a Wave Absorbing System Using a Liquefied Sandbed

J. Ocean Eng. Technol. 2006;20(4):9-16.

Kang, Yoon-Koo;Takahashi, Shigeo;

Port Management Team, Engineering & Construction Group, Samsung Cporporation;Port and Airport Research Institute;

Keywords: Liquefied sandbed, Wave absorbing system, Wave damping, Water supply pipes, Wave-induced sandbed compaction

Abstract

A new wave-absorbing system, called the liquefied sandbed wave barrier (LSWB) system, is currently under development at the Port and Airport Research Institute (PARI) of Japan. The wave damping effect by the LSWB system is substantial, as confirmed by small-scale experiments and FEM numerical calculations, i.e., the wave transmission coefficient of the system is less than 0.2. Here, the results of large-scale experiments arediscussed in view of practical application. Although the LSWB system provides high wave damping, nearly equal to theoretical values, difficulty exists in obtaining a homogeneously liquefied sandbed, due to the occurrence of liquefied sandbed compaction by cyclic wave loading, which in turn, reduces excess pare pressure and the wave damping effect. These two phenomena primarily occur when the sandbed is composed of fine sand with small permeability. Based on experimental results, we propose a design method that includes countermeasures against such problems, and a prototype LSWB system is constructed in a very large wave flume at PARI. Wave damping by the prototype LSWB system is confirmed to be quite stable and high, as predicted by theoretical calculations.