Seismic Behavior of an Underlying Alluvial Clay on Man-Made Islands During the 1995 Hyogoken-Nambu Earthquake

Abstract

ABSTRACT The authors have studied the seismic behavior of the alluvial clay layer on Kobe Port Island during the 1995 Hyogoken-Nambu earthquake. First the shear stress-strain relationship of the clay was estimated from the main shock of seismic array data. Next using the stress wave inferred from array records we conducted a cyclic simple shear test. The samples used in this study were the clay sampled from Port Island and Rokko Island. The clay sampled from the two man-made islands are from the same clay layer, but the clay from Rokko Island was not as consolidated as the clay at Port Island. After consolidation with the confining pressure at the array site, we applied a dynamic shear stress at the same stress rate as the actual earthquake. The shear strain time histories inferred from array records were compared with those from the simple shear test. The strain time history obtained from the simple shear test gave good comparison to that obtained from array records. Finally the settlement due to dynamic shearing was studied through the simple shear test. It was found that the difference of the degree of consolidation affects the seismic behavior of soft clay.