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

为了研究砂层对面波传播的液化敏感性，首先考虑了地基对瑞利波和乐夫波的响应。在这种情况下，土体单元受到主应力的旋转，因此研究了砂土在主应力旋转过程中的剪切行为。为了得到砂土在更大应力状态下的剪切特性，基于双滑移理论提出了散体材料的本构关系。在此基础上，提出了以有限元分析的形式对液化强度进行预测的方法，并通过对日本地震液化场地地脉动的观测，检验了软弱表层的响应，讨论了地脉动特征与地基结构的关系。在此基础上，研究了神谷县南部县地震的强震记录，确定了面波的影响。由此可见，面波对震害有很强的影响，尤其是在地震记录中间出现的0.5s分量上。强度为Vi的聚焦区部分归因于层状软砂的面波响应。最后，通过有限元分析验证了面波对体波的贡献，并通过一个模型地面讨论了产生面波的具体位置。

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.