Untitled

Abstract

After the East Groin of Ishikari Bay New Port subsided, we gathered data on the average caisson height and on the significant wave height measured at the surface where the water depth was 24 m in the sea offshore of the port. These two types of data were compared to investigate the relationship between the subsidence and waves. Also, we examined the causes of the subsidence and countermeasures based on the results of post-subsidence surveys, including an onsite survey. The examination revealed that when high waves cause subsidence that progresses to some extent, there was no major subsidence after that extent. The post-subsidence soil survey confirmed that the scour occurred after the subsidence. The onsite survey indicated that mat installation was an effective countermeasure against scour.