To prevent slip in the case of a slope with a weak layer, prevention piles are installed as a countermeasure. However, although the stability evaluation of slopes with prevention piles has been proposed, it has not been fully verified. Therefore, in order to verify the stability of a soft rock slope reinforced by prevention piles, a centrifugal model test and numerical simulations were carried out.

When performing dynamic nonlinear analysis on soft rock slopes against large-scale earthquakes, tensile failure frequently occurs in the vicinity of the surface layer. Furthermore, in the case of a slope with a weak layer and prevention piles, it is assumed that tensile failure will occur at the upper part of the weak layer and front part of the prevention piles. When the shear strength and tensile strength are equally reduced to the residual strength, there is a possibility that the simulation results are highly conservative. Originally, introducing the anisotropy of strength and rigidity after failure made it easier to reproduce model test results. However, in dynamic simulations, this is extremely difficult because the conditions change from one moment to the next.

Based on this background, in this study, modeling was performed via dynamic nonlinear analyses as a strength characteristic after tensile failure of soft rock by considering the handling of strength after tensile failure. We also focused on the initial shear modulus of the weak layer. The applicability of dynamic nonlinear analyses was considered from the viewpoint of the reproducibility of collapse behavior targeted for the centrifugal model test, which assumed the countermeasure of installing prevention piles in a cut slope with a weak layer.

1. Introduction

The seismic resistance of slopes must be improved to protect the important facilities of nuclear power plants. Toward this, countermeasure construction such as the use of prevention piles is sometimes carried out (Nuclear Standards Committee of JEA 2016). Although seismic stability evaluation methods for slopes reinforced by prevention piles have been proposed (Toda et al. 2013), the effectiveness of the flow of stability evaluation has not been sufficiently verified, as it is difficult to ascertain the behavior of the actual slope at the time of collapse as a result of the installed prevention piles. In order to verify the flow, a dynamic centrifugal model experiment was carried out on a model slope reinforced by prevention piles (Kobayakawa et al. 2019).

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