Rock debris is considered a stable material suitable for use as a structural foundation. Therefore, embankments had been constructed on reclaimed ground composed of rock debris as seawalls against tsunamis at a Japanese nuclear power plant. Despite this perceived stability, the recent strengthening of seismic design requirements for Japanese nuclear power plants has made it necessary to evaluate the liquefaction potential of reclaimed grounds, including those constructed with rock debris. Moreover, because reclaimed grounds consisting of rock debris frequently exhibit heterogeneity, seismic evaluations of the seawall must account for effects of spatial variability in the liquefaction resistance of the reclaimed ground consisting of rock debris more appropriately. This study investigated the effects of this spatial variability on the geotechnical properties of reclaimed ground composed of rock debris beneath an embankment using centrifuge model tests and corresponding numerical simulations. The centrifuge models incorporated 29.3% weak zones characterized by reduced liquefaction resistance. Constitutive model parameters were derived from laboratory test results. Consistent with the centrifuge test outcomes, the numerical simulations demonstrated that variations in the spatial arrangement of weak zones had a limited effect on overall embankment settlement. Furthermore, employing weighted average ground properties based on the volumetric proportion of weak zones in the simulations effectively reproduced the observed settlement behavior. Although the centrifuge model tests were conducted under controlled conditions with the proportion of weak and normal zones known in advance, the results of this study contribute to more rational setting of input parameters in numerical analyses for reclaimed ground consisting of heterogeneous rock debris.
Ishimaru et al. (Thu,) studied this question.