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A comparison of small strain stiffness in till as measured by seismic refraction and barometric loading response
Date Issued
2018-06-12
Date Available
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.
Other Sponsorship
Department of Infrastructure NI
Construction Service DFPNI
Northern Ireland Railways
University of Saskatchewan
Engineering and Physical Sciences Research Council
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
Language
English
Status of Item
Peer reviewed
ISSN
1470-9236
This item is made available under a Creative Commons License
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