Evaluation of Liquefaction Potential of Gravelly Soil Layer Based on Field Performance Data

In general, gravelly soil layers are considered to be less susceptible to liquefy during earthquakes than sandy soil layers. However, in 1995 Hyogoken-Nambu Earthquake, sand ejection due to liquefaction was observed in Port Island and Rokkco Island, which were man-made islands reclaimed by gravelly soils. In this paper, firstly, site investigation including sampling by freezing technique was conducted in Rokko Island where lots of ejected sand was not observed during the earthquake to know liquefaction strengths of the reclaimed deposits. Secondly, earthquake response analyses were conducted for a site in Rokko Island as well as a site in Port Island to evaluate maximum stress ratios which were generated in the reclaimed deposits during the earthquake. Finally, relationships between maximum shear stress ratios during earthquakes and penetration resistance were investigated for liquefied sites and nonliquefied sites in the man-made islands