2024 年 10 巻 19 号 p. 704-709
This paper presents the results of a study to assess the effect of ground motion directionality on the stability of a slope under seismic loading. Stability conditions were determined through two-dimensional (plane strain) nonlinear dynamic analyses using the finite element method and the Newmark rigid block method. In the numerical calculations, the soil was characterized by a nonlinear elastoplastic constitutive model, including features such as small strain stiffness degradation, plastic straining due to primary compression, and a Mohr-Coulomb-type limit envelope. The adopted motions correspond to acceleration time histories recorded at rock outcrops. One of the selected records presents a horizontal particle motion that is significantly polarized and, therefore, directionality effects are expected to be more relevant. Analyses were performed following the so-called complete rotational approach, which implies the execution of calculations where the input motion is derived from the linear combination of the horizontal as-recorded components, accounting for different, non-redundant, incident angles. Obtained results provided relevant insights regarding the effects of ground motion directionality on the stability of slopes and showed that ignoring this aspect can lead to non-conservative evaluations. In addition, the comparison between the numerical nonlinear dynamic analyses and the Newmark method allowed us to broaden the interpretation of the results of the traditional rigid block method as a general stability index.
