Comparison of Wave Pressure on the Front Wall of the Caisson Breakwater without and with the Cap of Wave Chamber

摘要

This study experimentally investigated the change in distribution ofwave pressure on the front wall according to the existence of the capof the wave chamber of the perforated caisson breakwater. In order toobtain reliable experimental data, the measurement of wave pressurefor the non-porous caisson corresponding to zero porosity was firstcarried out and the results were compared with the well-knownpressure formula suggested by Goda(1974). The analysis showed thatthe measured pressure distribution fairly well agreed with the Godaformula, which confirmed the accurate measurement of wave pressurein the present experiment. Then, the experiment was performed forthe perforated caisson by varying the front wall porosity as well as theexistence of the wave chamber cap. The wave pressure distributionalong the porous front wall showed some noticeable differenceaccording to the porosity when there was cap of the wave chamber. Inaddition, the magnitudes of the total wave force estimated byintegration of the measured wave pressure showed markeddiscrepancy for the case without and with the cap of the wavechamber. In the latter case, in particular, significantly larger waveforces compared to the value based on Takahashi’s formula(Takahashi and Shimosako, 1994) were obtained influenced by thegentle air compression and subsequent burst phenomenon occurred inthe wave chamber. Further analysis is required for general applicationof this finding against various types of breakwater geometry and thewave conditions as well.