Numerical modelling of a structure with shallow strip foundation during earthquake-induced liquefaction

Abstract

Structures with shallow foundations are susceptible to excessive settlement and rotation in the event of earthquake-induced soil liquefaction. Numerical modelling of the problem remains challenging, due to persisting uncertainties regarding dynamic soil response and soil–structure interaction. In this paper, numerical simulations are employed to study the seismic response of a structure on a shallow mat foundation, resting on a liquefiable sand layer. A coupled hydromechanical analysis is performed employing the finite-differences code FLAC2D, modelling non-linear soil response with the constitutive model PM4Sand. A broad set of element tests on Hostun sand (widely used in centrifuge modelling) are performed and used for extensive model calibration. The calibrated model is then validated against centrifuge test results. The validation is not restricted to the recorded pore pressure, acceleration and settlement time histories, but extends to the deformation mechanisms extracted from centrifuge testing through image analysis, allowing for an in-depth assessment of the numerical simulation. Overall, the analysis is in good agreement with the centrifuge model test. The pore pressure build-up and the final foundation settlement and displacement fields are predicted with adequate accuracy. Although the accumulated displacements are well reproduced, the failure mechanism is not fully captured. This discrepancy is attributed to dissipation-related phenomena, which are not accurately reproduced in the numerical analysis.