Hydrodynamic pressures over modular porous reef breakwaters

Abstract

Low crested structures built with homogeneous stones or precast blocks serving the purpose of wave attenuation are often referred to as reef breakwaters. The present work involves laboratory investigation of hydrodynamic pressures exerted on reef breakwaters made of gabion boxes in submerged conditions. The study provides an understanding of nature and magnitudes of pressures in and around the reef structures depending on the configuration of choice. The knowledge on the wave induced pressure on porous structures is important to better understand the stability and flow around the coastal structures. Such reef based structures are also being adopted as mitigation against sea-level rise and to reduce loads exerted on existing maritime structures. The pressure reduction achieved on the leeside of the structure is also examined in the present study. This is of immediate interest for preserving the existing coastal structures in a serviceable condition, which are prone to more severe conditions than considered in the design. The wave-induced dynamic pressures on the submerged porous structure are analyzed and discussed in the present work for varying reef and wave parameters. This experimental study involves analysis of wave-induced pressure on the seaside, leeside and at the mid-section of the porous reef breakwaters. The investigation has been carried forward to bring out major parameters of concern for the present problem and their ranges. The study demonstrates that a pressure reduction of about 70% is achievable by the use of reef breakwaters and this clearly indicates the application of such structures for coastal resilience.