Seismic behaviour of shallow foundations on layered liquefiable soils

  • Daniele Bertalot

    Student thesis: Doctoral ThesisDoctor of Philosophy


    Earthquakes have been historically perceived as one of the most damaging
    natural hazards. Seismic soil liquefaction is often one of the major sources of
    damage and disruptions, and has been observed to severely affect key lifelines.
    Settlement and tilting of shallow foundations resting on saturated sandy/silty
    soils has been repeatedly observed throughout the world as a consequence of
    liquefaction or softening of the foundation soil. Such settlements and tilts can
    render structures unusable, and homes uninhabitable, causing significant economic losses. Despite the undoubted relevance of this phenomenon, field data on the liquefaction induced settlement of shallow foundations are scarce. New data from 24 buildings that suffered settlement and tilting as a consequences of soil liquefaction during the February 27th 2010 Maule earthquake in Chile, are presented in this work to supplement the existing field cases database. Due to the complexity of this phenomenon, field data are not suffcient to fully understand the mechanisms controlling the settlement of structures resting on liquefied or softened ground.In this framework, centrifuge modelling provides a valuable tool for research by reproducing field conditions in a controlled environment.
    A series of 10 dynamic centrifuge tests were performed as part of this work.
    Thanks to the University of Dundee newly installed centrifuge-mounted servohydraulic earthquake simulator, scaled version of field earthquake motions were reproduced in the models tested, enhancing the reliability of experimental
    results. Particular attention was given to the effect of key parameters on the
    observed foundation settlement. These parameters are the bearing pressure of
    the foundation, the thickness of the liquefied soil layer and the soil's relative
    density. The effect of the soil layering pattern was also investigated, with
    particular attention to the effect of a low permeability soil crust overlying the
    liquefied soil. Results suggest that the excess pore pressure generation in the
    foundation soil is significantly influenced by the stress distribution due to the
    presence of the foundation itself. In particular, lower excess pore pressure
    where measured in soil subjected to high static shear stresses (i.e. below the
    edge of a footing). The soil stratification pattern, and the relative thicknesses
    of the liquefied and un-liquefied portions of the soil profile, were also found to
    play a crucial role in determining the seismic demand at foundation level and
    the type of failure mechanism leading to foundation settlement.
    Observed differences between centrifuge (i.e. field) and element testing soil
    response are also discussed. Experimental results are compared to field observations, with the aim of improving the current understanding of the behaviour of structures built on shallow foundations in the eventuality of seismic induced liquefaction of their foundation soil.
    Date of Award2013
    Original languageEnglish
    SponsorsEngineering and Physical Sciences Research Council
    SupervisorAndrew Brennan (Supervisor)


    • Centrifuge modelling
    • Liquefaction
    • Shallow foundations
    • Layered soils
    • Earthquake

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