مهندسی عمران شریف (Nov 2019)
EXPERIMENTAL AND NUMERICAL MODELING ON SEISMIC RESPONSE OF LIQUEFIABLE SUB-LAYERS
Abstract
Soil liquefaction is caused by strong ground motion and causes loss of shear strength, lateral spreading, foundation failure, sand boiling and post-earthquake settlement. These liquefaction mechanisms have been studied intensively. Although the seismic site response is affected by the liquefiable soils, there is no comprehensive study of it in the technical literature due to the complexity of this issue. However, different physical and numerical modeling methods have been conducted to develop guiding principles for the seismic response analysis in liquefied sites. Nevertheless, some major restrictions pertain to these models such as ignoring the effects of the depth of liquefiable layer and unsuitable constitutive models. In this study, the seismic behavior of liquefiable sub-layers has evaluated what affects the seismic site response strongly. In this regard, using the shaking table model tests, the initial seismic response was obtained in the soil profile consisting of a liquefiable sub-layer. The sub-layers of the shaking table models were built with different densities, and the models were subjected to specific record motions of varying intensity. Acceleration and pore water pressure were measured in the soil profiles during all the tests. The influence of the liquefiable soil layers on the seismic site response during shaking was discussed comprehensively. Afterwards, in order to use the compatible constitutive model in numerical analysis, a series of 1D effective stress numerical models were employed, while the results were verified adequately with the results of the shaking table test. Note that the multi-yield surface model was utilized in the current study as a suitable constitutive model. Finally, the seismic response was processed, and the effect of the liquefied sub-layers on the seismic site response de-amplification was studied from different points of view. Consequently, experimental and numerical studies of this research showed that the liquefaction of sub-layers could effectively reduce the intensity of seismic waves and earthquake-induced force.
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