Abstract
A simplified method is proposed to evaluate the ground deformation due to liquefaction-induced flow. Under the assumption that liquefaction-induced flow occurs slowly after the main shaking, stress-strain relationship after liquefaction is obtained through the laboratory test in which sand sample is subjected to monotonic load after subjected to cyclic load causing liquefaction or more. Stress-strain curve is shown to be quite different from the conventional one under small strains. The curve is separated into small rigidity region and rigidity recovering region, and is modeled to be a bi-linear model. Rigidity in small rigidity region is evaluated both by laboratory test and back analysis of earthquake damage, and is expressed as the ratio to the initial modulus. The modeling of the ground other than liquefied layer, such as nonliquefied ground above the liquefied layer, is also proposed based on the back analysis of the earthquake damage. Three case studies are conducted: Showa-ohashi sate, Uozaki-hama site and Aoba-cho site that were damaged during the 1964 Niigata, 1995 Hyogoken-nambu, and 1983 Nihonkai-chubu earthquakes. The proposed method predicts liquefaction-induced ground deformation well.
