ELASTO-PLASTIC RESPONSE OF SLOPES DURING BIG EARTHQUAKES AND EVALUATION OF RESIDUAL DEFORMATION

基于极限平衡法的边坡地震稳定性分析的解有时是非常保守的，因为这种方法假定地震力是持续作用的，并且没有考虑响应的放大。另一方面，也证实了动力弹塑性有限元法等数值分析方法对边坡地震稳定性的评价是非常有效的。本文基于φ=0材料的剪切模量Go和不排水剪切强度cu，提出了一种新的循环加载模型。该模型的一个优点是G-γ和h-γ的关系得到了适当的考虑。采用该模型建立的二维动态弹塑性有限元模型可以较好地模拟软粘土地基上的路堤动态离心模型试验。在本研究的第二阶段，建立了考虑摩擦角φ的模型。提出了边坡动态离心试验的有限元模拟方法。将水平加速度作用于地基基底，测量边坡的响应。试验后观察到残余变形，并伴有明显的滑移面。用二维动弹塑性有限元法对模型边坡离心试验结果进行了较好的模拟。本研究提出的循环荷载模型对于边坡的实际抗震设计是非常有效的，因为模型中使用的参数数量非常少。该模型基于Rowe的应力-剪胀关系考虑了剪胀效应，在不久的将来有可能应用于土壤液化问题。

Solutions derived from a seismic stability analysis for slopes, based on the limit equilibrium method, are sometimes very conservative, because the seismic force is assumed to be acting constantly and the amplification of response is not taken into account in such methods. On the other hand, it has been confirmed that the numerical analysis such as the dynamic elasto-plastic FEM is very effective for the evaluation of the seismic stability of slopes. In this study, a new cyclic loading model is proposed, based on the shear modulus Go and the undrained shear strength cu for φ=0 materials. An advantage of this model is that the G-γ and h-γ relationships arte properly taken into account. The 2D dynamic elasto-plastic FEM with this model could simulate well a dynamic centrifuge model test of an embankment on the soft clayey ground.In the second stage of this study, this model is developed to take into account the friction angle φ as well. A finite element simulation for dynamic centrifuge test of a slope is presented. The horizontal acceleration was applied to the base of the ground, and the response of the slope was measured. The residual deformation, accompanied with a clear slip surface, was observed after the test. The results observed in the centrifuge test for the model slope were simulated well by the 2D dynamic elasto-plastic FEM.The cyclic loading model proposed in this study was found to be very effective for the actual seismic design of slopes, because the number of parameters used in the model is very low. This model can consider the dilatancy effect based on the Rowe's stress-dilatancy relationship, having the possibility of its application to soil liquifaction problems in the near future.