A Study on A Method of Prediction of Liquefaction Susceptibility of Sandy Ground during Surface Wave Propagation

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In order to investigate the liquefaction susceptibility of sand layr due to surface wave propagation, response of the ground to Rayleigh wave and Love wave was firstly considered. In these cases soil element is subjected to rotation of principal stress and therefore shear behavior of sand during principal stress axs rotaion was studied. For the purposes of obtaining the shear behavior of sand under more ganeralized stress states constitutive relations of granular materials were proposed based on double slip theory. From these results a predictive method of liquefaction strenght was proposed in the form of FEM analyzes.Response of the soft surface layrs were examined by measuring the micro tremor at the sites of liquefied area by the Nihonkai Earthquake, and relation between micro tremor characteristics and ground structures were dicussed. Then the strong motion records observed by the Hyougoken Nammbu Earthquake were studied and effct of surface waves were determined. From the consideration obtained it is obvious that the surface wave has strong effects on the damage especially in the components of 0.5 sec which appears in the middle of earthquake records. The focussed area of intensity VII are partly attributed to the surface wave response of the layred soft sand. Finally contribution of surface waves to body waves are checked by the FEM analyzes and the specific site of generating the surface waves are discussed by a model ground.