It is satisfied with the Nuclear Regulation in Japan to estimate slope failures in case of a huge earthquake using an equivalent linear analysis. However, in term of the risk assessment and the accident management as an electric company, it is necessary to estimate which area of slopes collapses, and how much ground slides. Therefore, we compared the dynamic model tests using cut rock slope models with equivalent linear analysis and time-history nonlinear analysis from the viewpoint of reproducibility of the collapse behavior and the collapse area. As a result, the equivalent linear analysis proved to have a certain margin in the evaluation of the slip safety factor. However, the slip surface with the minimum slip safety factor did not coincide with the actual collapse range. On the other hand, time-history nonlinear analyses were able to reproduce the residual displacement of the slope model. Furthermore, the accumulation area of strain and the collapse range of the slope model generally agreed

1 Introduction

For important facilities of nuclear power plants, it is necessary to evaluate the stability of the surrounding slope at the time of earthquake. Because it is necessary to confirm that the safety function of the facility is not seriously affected when the surrounding slope collapses due to the earthquake.

In the guide(Nuclear Regulation Authority.2013) established with the new regulation for the nuclear power reactor, the stability of the slope is considered to confirm that the safety factor against sliding defined as the ratio of resistance of the slope material to sliding force of ground on the slip surface is 1.2 or more by dynamic analysis. And equivalent linear analysis by finite element method is generally used as dynamic analysis (Japan Electric Association Guide. 2015). However, a slip safety factor of less than 1 and a slope collapse are not necessarily equivalent (Ishimaru et al 2011).

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