Dynamic response analysis is conducted to evaluate slope stability under seismic conditions for the surrounding slope at important structures such as main traffic routes, nuclear power plants etc. Stability analyses have generally used numerical analysis assuming that rock mass is elastic and homogeneous using the results from PS logging and/or the seismic coefficient method. However, the behavior of rock masses is greatly influenced by the geometrical distribution of discontinuities within the rock mass.

The authors have proposed Multiple Yield Model (MYM), which is a type of finite element method constituting the mechanical properties of intact rock and discontinuity systems in a rock mass and introducing cyclic loading elastic-plastic deformation characteristics of rock joints. The applicability of this method was verified by making comparisons with the observed seismic waves in rock foundations under large structures during the 2011 Off the Pacific Coast of Tohoku earthquake and so on (Iwata et al., 2013). We indicate the necessity of considering discontinuities in rock masses on modeling of seismic response analysis.

In this study, we conducted seismic response analysis of rock slopes using MYM and evaluated the influence of the geometrical distribution of discontinuities, such as dip angle and number of joint sets, and compared them with the traditional model described above. As a result, seismic response is strongly influenced by the distribution of discontinuities and the seismic response of MYM is distinctly different from one of elastic body. To assess the seismic response of a slope under earthquake conditions, it is necessary to conduct numerical analysis which considers the distribution and mechanical properties of discontinuities.

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