Influence of axial load on lateral pile response in liquefiable soils Part I: physical modelling

J.A. Knappett, S. P. G. Madabhushi

    Research output: Contribution to journalArticle

    20 Citations (Scopus)

    Abstract

    Current research work into the behaviour of piled foundations in liquefiable soils has concentrated on the response to lateral inertial and kinematic loads. It has recently been demonstrated in the literature, however, that an alternative mechanism exists, whereby piles carrying significant axial loads may become unstable as lateral soil restraint is lost owing to earthquake-induced soil liquefaction. In the work presented here and in a companion paper, this effect is examined in greater depth, particularly regarding the integration with and effects on the lateral response of piles such that the two effects can be treated under a unified framework. Dynamic centrifuge testing was used to investigate pile instability by examining the behaviour of pile groups with lateral deflections. Amplification of these deflections was observed to occur during liquefaction, although currently available simple idealisations of soil behaviour were found greatly to over-predict these amplifications when compared with the experimental observations. The response of the soil to such large-deformation events was determined for use in more sophisticated numerical modelling presented in the companion paper. Relative pile-soil flexibility was found to have a strong influence on amplifications occurring in the tests. Ultimately, at high axial load or amplification, unstable collapse ( bifurcation) was found to occur both during earthquake shaking, and afterwards owing to excess pore pressure migration altering the strength of the supporting soil surrounding the piles.

    Original languageEnglish
    Pages (from-to)571-581
    Number of pages11
    JournalGéotechnique
    Volume59
    Issue number7
    DOIs
    Publication statusPublished - Sep 2009

    Keywords

    • centrifuge modelling
    • deformation
    • earthquakes
    • failure
    • liquefaction
    • piles
    • BENDING MOMENT EVALUATION
    • SINGLE PILES
    • SPREADS

    Cite this

    @article{b6fad4c60be24fa583d6b519bb433eb3,
    title = "Influence of axial load on lateral pile response in liquefiable soils Part I: physical modelling",
    abstract = "Current research work into the behaviour of piled foundations in liquefiable soils has concentrated on the response to lateral inertial and kinematic loads. It has recently been demonstrated in the literature, however, that an alternative mechanism exists, whereby piles carrying significant axial loads may become unstable as lateral soil restraint is lost owing to earthquake-induced soil liquefaction. In the work presented here and in a companion paper, this effect is examined in greater depth, particularly regarding the integration with and effects on the lateral response of piles such that the two effects can be treated under a unified framework. Dynamic centrifuge testing was used to investigate pile instability by examining the behaviour of pile groups with lateral deflections. Amplification of these deflections was observed to occur during liquefaction, although currently available simple idealisations of soil behaviour were found greatly to over-predict these amplifications when compared with the experimental observations. The response of the soil to such large-deformation events was determined for use in more sophisticated numerical modelling presented in the companion paper. Relative pile-soil flexibility was found to have a strong influence on amplifications occurring in the tests. Ultimately, at high axial load or amplification, unstable collapse ( bifurcation) was found to occur both during earthquake shaking, and afterwards owing to excess pore pressure migration altering the strength of the supporting soil surrounding the piles.",
    keywords = "centrifuge modelling, deformation, earthquakes, failure, liquefaction, piles, BENDING MOMENT EVALUATION, SINGLE PILES, SPREADS",
    author = "J.A. Knappett and Madabhushi, {S. P. G.}",
    year = "2009",
    month = "9",
    doi = "10.1680/geot.8.009.3749",
    language = "English",
    volume = "59",
    pages = "571--581",
    journal = "Geotechnique",
    issn = "0016-8505",
    publisher = "Thomas Telford Ltd.",
    number = "7",

    }

    Influence of axial load on lateral pile response in liquefiable soils Part I : physical modelling. / Knappett, J.A.; Madabhushi, S. P. G.

    In: Géotechnique, Vol. 59, No. 7, 09.2009, p. 571-581.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Influence of axial load on lateral pile response in liquefiable soils Part I

    T2 - physical modelling

    AU - Knappett, J.A.

    AU - Madabhushi, S. P. G.

    PY - 2009/9

    Y1 - 2009/9

    N2 - Current research work into the behaviour of piled foundations in liquefiable soils has concentrated on the response to lateral inertial and kinematic loads. It has recently been demonstrated in the literature, however, that an alternative mechanism exists, whereby piles carrying significant axial loads may become unstable as lateral soil restraint is lost owing to earthquake-induced soil liquefaction. In the work presented here and in a companion paper, this effect is examined in greater depth, particularly regarding the integration with and effects on the lateral response of piles such that the two effects can be treated under a unified framework. Dynamic centrifuge testing was used to investigate pile instability by examining the behaviour of pile groups with lateral deflections. Amplification of these deflections was observed to occur during liquefaction, although currently available simple idealisations of soil behaviour were found greatly to over-predict these amplifications when compared with the experimental observations. The response of the soil to such large-deformation events was determined for use in more sophisticated numerical modelling presented in the companion paper. Relative pile-soil flexibility was found to have a strong influence on amplifications occurring in the tests. Ultimately, at high axial load or amplification, unstable collapse ( bifurcation) was found to occur both during earthquake shaking, and afterwards owing to excess pore pressure migration altering the strength of the supporting soil surrounding the piles.

    AB - Current research work into the behaviour of piled foundations in liquefiable soils has concentrated on the response to lateral inertial and kinematic loads. It has recently been demonstrated in the literature, however, that an alternative mechanism exists, whereby piles carrying significant axial loads may become unstable as lateral soil restraint is lost owing to earthquake-induced soil liquefaction. In the work presented here and in a companion paper, this effect is examined in greater depth, particularly regarding the integration with and effects on the lateral response of piles such that the two effects can be treated under a unified framework. Dynamic centrifuge testing was used to investigate pile instability by examining the behaviour of pile groups with lateral deflections. Amplification of these deflections was observed to occur during liquefaction, although currently available simple idealisations of soil behaviour were found greatly to over-predict these amplifications when compared with the experimental observations. The response of the soil to such large-deformation events was determined for use in more sophisticated numerical modelling presented in the companion paper. Relative pile-soil flexibility was found to have a strong influence on amplifications occurring in the tests. Ultimately, at high axial load or amplification, unstable collapse ( bifurcation) was found to occur both during earthquake shaking, and afterwards owing to excess pore pressure migration altering the strength of the supporting soil surrounding the piles.

    KW - centrifuge modelling

    KW - deformation

    KW - earthquakes

    KW - failure

    KW - liquefaction

    KW - piles

    KW - BENDING MOMENT EVALUATION

    KW - SINGLE PILES

    KW - SPREADS

    U2 - 10.1680/geot.8.009.3749

    DO - 10.1680/geot.8.009.3749

    M3 - Article

    VL - 59

    SP - 571

    EP - 581

    JO - Geotechnique

    JF - Geotechnique

    SN - 0016-8505

    IS - 7

    ER -