A Study on Effects of Earthquake Ground Motion and Subsoil Conditions on Liquefaction of Sandy Ground

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Because the fiscal year of 1998 was the last year of this research project, all the researchers of this research group tried to contact each other to keep the good relationship between articles and concentrated to bring their research works to conclusions. The head investigator studied relationship between input earthquake characteristics and liquefaction indices such as degree plasticity and accumulated dissipation energy, and found out the relation between nonlinear behaviors of soil layers due to liquefaction and the seismic parameters such as maximum velocity and maximum response velocity spectrum using the seismic records obtained during the Kobe EarthquakeInvestigators studied on the method of estimation of earthquakes for the design of structures considering the amplification by the surface subsoil and non-stationality of the seismic waves in terms of nonlinearity appeared in the velocity response spectra. A nonlinear incremental constitutive model was also proposed for the three dimensional stress state needed for the liquefaction analyses, which is applicable even to deformation under the stress conditions of rotating principal stresses. To evaluate the actual deformation characteristics, a large scale simple shear apparatus was developed and several tests were performed on the soils containing cobbles and boulders and fundamental deformation characteristics such as dilatancy behaviors and shear strength were studied.