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Structures with shallow foundations resting on liquefiable layers can suffer excessive settlement in the event of an earthquake. The state of practice often estimates the settlement of structures using empirical methodologies. Commonly, these are based on case histories or estimations developed for the free-field. Their reliability has been contested due to uncertainties regarding the dominant deformation mechanisms in the presence of a structure. Here, six dynamic centrifuge tests are presented, investigating the response of structures with shallow foundations resting on liquefiable layers of different thickness. Particle Image Velocimetry (GeoPIV) was used to capture the developed deformation mechanisms. A structure resting on a deep liquefiable layer was found to settle primarily due to increased lateral soil displacements taking place beneath a bulb of stiffer soil formed below the foundation. In shallower layers, this bulb reached the base of the layer, transmitting large accelerations to the structure and promoting a rocking response. Settlement in this case was generated due to increased soil displacement from under the edges of the foundation. In no case were methodologies aimed for the free-field able to account for the salient settlement-generation mechanisms.

Loosely packed sand that is saturated with water can liquefy during an earthquake, potentially causing significant damage. Once the shaking is over, the excess pore water pressures that developed during the earthquake gradually dissipate, while the surface of the soil settles, in a process called post-liquefaction reconsolidation. When examining reconsolidation, the soil is typically divided in liquefied and solidified parts, which are modelled separately. The aim of this paper is to show that this fragmentation is not necessary. By assuming that the hydraulic conductivity and the one-dimensional stiffness of liquefied sand have real, positive values, the equation of consolidation can be numerically solved throughout a reconsolidating layer. Predictions made in this manner show good agreement with geotechnical centrifuge experiments. It is shown that the variation of one-dimensional stiffness with effective stress and void ratio is the most crucial parameter in accurately capturing reconsolidation.