Multiscale modelling of the seismic response of shallow foundations on saturated granular soils

ABSTRACT This paper presents a multiscale approach to analyse the seismic response of a spread-footing system founded on saturated granular soil deposits that might be susceptible to liquefaction. The pore-fluid is idealised as a continuum by using a homogenised form of Navier-Stokes equations that accounts for the presence of the solid particles. These particles are modelled at a microscale using the discrete element method. The foundation is idealised as a square rigid block by generating a group of glued particles. Computational simulations were conducted to investigate the response of spread-footings on saturated deposits when subjected to a seismic excitation. For the considered closely-spaced foundation system, it is possible to have a foundation settlement smaller than the free-field. Stress overlap between neighbouring footings could lead to an increase in soil stiffness and less susceptibility to pore-pressure build-up and volume decrease compared with the free-field. The majority of the foundation settlement occurs during shaking, whereas settlement continues to accumulate post shaking in the free-field. Evaluation of the contribution of base and lateral walls of the foundation to the lateral response of the footing showed that the predominant contributors were the base shear force and walls normal to the direction of shaking.