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

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Title: A comparison of small strain stiffness in till as measured by seismic refraction and barometric loading response
Authors: Kelly (Harley), R.M.G.
Bergamo, P.
Hughes, D.A.B.
Donohue, Shane
et al.
Permanent link: http://hdl.handle.net/10197/10560
Date: 12-Jun-2018
Online since: 2019-05-21T08:29:02Z
Abstract: 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. Characterization 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. 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 characterizing 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 summarizes the results of field trials within a cutting in stiff till in Northern Ireland in which these two techniques were used to characterize small strain stiffness.
Type of material: Journal Article
Publisher: Geological Society of London
Journal: Quarterly Journal of Engineering Geology and Hydrogeology
Volume: 51
Issue: 4
Start page: 493
End page: 502
Copyright (published version): 2018 the Authors
Keywords: Geotechnical engineeringBarometric loading efficiencyGeophysicsSurface wave surveySmall strain stiffnessLodgement till
DOI: 10.1144/qjegh2017-040
Other versions: http://qjegh.lyellcollection.org/content/51/4/493
Language: en
Status of Item: Peer reviewed
Appears in Collections:Civil Engineering Research Collection

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