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.