A comparison of small strain stiffness in Till as measured by seismic refraction and barometric loading response

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    Soil Stiffness can vary over several orders of magnitude depending on the actual range of strain imposed by testing, or as a result of operational strains in geotechnical structures. Soil stiffness changes rapidly with strain level at low strain levels (0.01–0.1%) and the variation with strain is not linear. Characterisation of the in situ small strain stiffness of stiff soils is important in geotechnical design; however, analyses of the mechanical behaviour of these soils is confounded by stiffness values that vary with strain level.Harley et al. (2016) demonstrate how stiff till cuttings are susceptible to progressive failure as a result of strain softening. As a consequence, the evolution of stiffness during progressive failure is both a key parameter in characterising pre-failure slope deformations and a key diagnostic of softening. Changes in strength (due to softening) should be reflected in commensurate temporal and spatial changes in stiffness; consequently, real-time, in situ measurements of stiffness would better define the progression of softening.Seismic surveys, which create small compression and shear strains, have been used to estimate in situ small strain elastic moduli. These spatially extensive measurements can be correlated to temporal variations in stiffness from the monitoring of barometric loading efficiency. In this latter method, the pore pressure response of a grouted (sealed) piezometer to barometric pressure fluctuations is used to measure the compressibility (stiffness) of the formation. This article summarises the results of field trials within a cutting in stiff till in Northern Ireland in which these two techniques were used to characterise small strain stiffness.

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    • A comparison of small strain stiffness in Till as measured by seismic refraction and barometric loading response

      Rights statement: © 2018 The Author(s). Published by The Geological Society of London. This work is made available online in accordance with the publisher’s policies. Please refer to any applicable terms of use of the publisher.

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      Embargo ends: 28/09/2019

    DOI

    Original languageEnglish
    Pages (from-to)493–502
    JournalQuarterly Journal of Engineering Geology and Hydrogeology
    Journal publication dateNov 2018
    Issue number4
    Volume51
    Early online date28 Sep 2018
    DOIs
    Publication statusPublished - Nov 2018

    ID: 160570118