Evaluation of Seismic Response of Rectangular Underground Structures in Liquefiable Soils

Abstract

AbstractThe evaluation of the seismic response of underground structures is an important step in its design. Currently, displacement-based pseudo static methods are one of the most popular class of methods recommended by several design guidelines and codes. However, in this study, through comparisons with dynamic finite element method analysis using advanced soil constitutive models, we show that the application of the simplified displacement-based method in liquefiable soils is inappropriate. The seismic response of a typical rectangular section underground structure in non-liquefiable and liquefiable ground using linear elastic model and the unified constitutive model for large post-liquefaction deformation of sand, respectively. A displacement-based pseudo static method is then used in these two scenarios, using input from free field analysis. Comparisons between the results from the two types of analysis methods show relatively good agreement for the non-liquefiable ground scenario. Whereas for the liquefiable ground case, the displacement-based method significantly underestimates the deformation and internal forces of the structure. This is shown to be caused by the ineptness of the displacement-based pseudo static method in taking into consideration the spatial non-uniformity of structure and near field soil seismic response in liquefiable ground. This study highlights the importance of advanced constitutive modeling of soils in practical geotechnical earthquake engineering applications.KeywordsUnderground structureLiquefiable soilPseudo-static analysisDynamic finite element methodConstitutive model