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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.

The rapid evolution of 3D-printing has sparked interest for possible applications in geotechnical research. This paper investigates the use of 3D-printing to create an artificial granular medium that reproduces the morphological characteristics of a natural sand. Initially, individual particle geometries are captured from the reference sand using micro CT scanning. Subsequently, their capacity to represent the morphology of the original medium is assessed.An evaluation of 3D-printing options ensues, leading to the selection of PolyJet as the currently preferential technology. Post-printing, micro CT scanning reveals that only particles of diameter of 2 mm or larger can be reliably reproduced using PolyJet. Finally, 3D-printed media are assessed for their performance in possible geotechnical applications by examining their hydraulic conductivity using a constant head permeameter and their shear response using drained triaxial compression tests.

Earthquake-induced liquefaction is typically viewed as an undrained phenomenon with undrained element tests forming the core of knowledge built around it. However, there is evidence to suggest that partial drainage could be taking place during an earthquake. In this paper two dynamic centrifuge tests are presented, in which drainage was restricted for a part of the soil by enclosing it within a chamber, in order to assess its importance. The hypothesis of undrained behaviour was found to be inappropriate for liquefied sand, even within the timescale of an earthquake. Fluid flow during the seismic motion was inevitable. Its effect on pore pressures and shear stress–shear strain response was controlled by the proximity of the boundaries.

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.

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The scaling laws that arise from dynamic centrifuge modelling contain an inconsistency between the scaling of time for dynamic events and diffusion events. This problem can be resolved by reducing the permeability of the soil, with the help of high viscosity pore fluids. Hydroxypropyl methylcellulose is a water soluble cellulose ether that is widely used to create such fluids. In this paper, the effects that concentration, temperature, ageing, and shearing rate have on the viscosity of hydroxypropyl methylcellulose solutions are examined and equations that quantify them are presented. This information is meant to act as a guideline in preparing high viscosity pore fluids for dynamic centrifuge tests.