2024 年 10 巻 23 号 p. 848-853
Simplified liquefaction assessment procedures have been widely used to estimate the severity of liquefaction under earthquake loading, which is often confirmed by the presence of sand boils. Back analyses of case studies have shown that the simplified assessment procedures can overestimate or underestimate the liquefaction potential of a deposit (i.e. false positives and false negatives respectively). The occurrence and severity of sand boils are highly dependent on the soil permeability and the hydro-mechanical interaction of cross-layers (system response effects), which the simplified liquefaction assessment procedures do not account for. Additionally, the variation of hydraulic conditions during and after the earthquake shaking significantly affects the evolution of sand boils. In this study, the layered system effects on liquefiable deposits are examined through dynamic nonlinear effective stress analysis. Scenarios where a liquefiable layer is interbedded within materials of distinct hydro-mechanical characteristics are examined parametrically employing the fully coupled (u-p) finite element software PLAXIS. The influence of the presence and the characteristics of non-liquefied or low-permeability layers surrounding the liquefiable layer on the development of sand boils is investigated.
