Seismic performance and mitigation strategies for soil-foundation-structure systems on liquefiable soils

Abstract

• A soil–foundation–structure (SFS) system on layered liquefiable soil was numerically modeled to assess seismic performance. • Key parameters included liquefiable soil relative density, layer depth, groundwater level, ground inclination, and foundation depth. • Increasing these parameters reduced foundation settlement and rotation but amplified acceleration and structural shear force. • Greater foundation depth could be one of the most effective mitigation strategy, although trade-offs between beneficial and detrimental responses should be considered in design. Fully coupled three-dimensional dynamic nonlinear FE analysis was conducted to investigate the comprehensive behavior of the soil–foundation–structure (SFS) system resting on stratified liquefiable ground. Parametric models were developed using the TCL scripting language and executed within the OpenSeesSP framework. The numerical framework was initially validated against centrifuge test results for an SFS system founded in liquefiable sand, after which it was employed to examine the effects of several governing parameters on seismic performance under representative earthquake motions. These key parameters include the relative density of liquefiable layer ( D r ), liquefiable layer depth ( D L ), groundwater table ( H w ), ground inclination of soil layers ( S ), foundation depth ( D f ), peak ground acceleration (PGA), and frequency content of earthquake. In particular, the influences on the excess pore pressure, acceleration, settlement, maximum lateral displacement (MLD), structural shear force, and drift were evaluated. The results showed that foundation settlement and rotation decreased, while acceleration was amplified at the foundation level with the increased key parameters (except for D L ). The structural MLD and shear force increased with D r , H w , and S ; conversely, MLD decreased with an increase in D L and D f . Among the examined mitigation strategies, increasing the D f exhibited the strongest mechanical influence in reducing foundation settlement, MLD, rotational response, and overall structural drift. The liquefiable layer compaction and increasing H w are recommended as the next priorities. The compaction strategy reduces settlement, lateral displacement, and foundation rotation but increases structural drift and shear force. Therefore, the trade-off between beneficial and detrimental responses should be considered in its design and practical implementation. Ignoring even a small ground inclination can lead to underestimation of MLD and drift, but its impact on foundation rotation and settlement is approximately low.

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