Liquefaction of improved ground at Port Island, Japan, during the 1995 Hyogoken-nanbu earthquake

摘要

Liquefaction at an improved ground in Port Island, a man made island in Japan, during the 1995 Hyogoken-nambu earthquake is presented. The site was improved by the rod compaction method, and neither significant structural damage nor ground deformation was observed at the time of the earthquake. Detailed insitu and laboratory tests were conducted at the site, which included dynamic deformation test and liquefaction strength test of frozen samples. In-situ investigation pointed out that the ground settlement of about 10 cm occurred during the earthquake. Two effective stress earthquake response analyses were conducted using the data from in-situ and laboratory tests. Both calculations showed that the ground near the water table did not liquefy, but the ground 7 meters below the ground surface (4 meters below the water table) liquefied. This result is in consistent witht he observed fact.