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

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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.