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Article: Influence of strain rate and acceleration on the behaviour of reconstituted clays at small strains

TitleInfluence of strain rate and acceleration on the behaviour of reconstituted clays at small strains
Authors
KeywordsClays
Creep
Dynamics
Laboratory tests
Stiffness
Time dependence
Issue Date2010
PublisherThomas Telford (ICE Publishing). The Journal's web site is located at http://www.geotechnique-ice.com
Citation
Geotechnique, 2010, v. 60 n. 10, p. 751-763 How to Cite?
AbstractThis paper attempts to bridge the gap between the wellknown characteristics of strain rate-independent elastic stiffness and of the time-dependent behaviour of clays at large strains. Effects of acceleration, strain rate and ageing are examined in the very small to small strain region, using results from tests on reconstituted London Clay and kaolin. Static measurements of the shear modulus at small strains, using local instrumentation, indicate that the shear modulus is rate-independent when the soil is subjected to elastic deformations only. Most often, in practice, soil specimens are left to rest between the compression and shearing stages, until deformations associated with creep become negligible. The testing strain rate imposed upon shearing induces a temporary acceleration of strains, which results in very high measured stiffnesses. Test data show, however, that when the shearing axial strain rate is of the same order of magnitude as that measured at the end of the compression/creep stage, the remaining plastic creep strains influence the measured stiffness, which is then measured to be comparatively low. Test data also seem to show that temporary strain acceleration may hide effects of recent stress path rotation. Additionally, bender element tests were performed during isotropic compression tests with changes in stress rate and creep stages. The data indicate that the strain rate affects the value of the dynamic shear modulus of the soil. It is suggested that the increase in dynamic shear modulus during short-term creep is caused by mechanisms linked to the gradual decrease in strain rate during creep, but further investigation would be needed to clarify which physical mechanisms. A new method to account for strain rate in evaluating the dynamic shear modulus of normally consolidated reconstituted clays is finally proposed.
Persistent Identifierhttp://hdl.handle.net/10722/137228
ISSN
2015 Impact Factor: 2.0
2015 SCImago Journal Rankings: 2.837
ISI Accession Number ID
Funding AgencyGrant Number
Engineering and Physical Sciences Research Council (EPSRC)
Funding Information:

The authors would like to thank Imperial College for providing the rotary cores of undisturbed London Clay, without which this research could not have been carried out, and Dr Coop for his guidance and help with the experimental testing at the start of the research. The authors are also very grateful to Dr Joao Rio and Mr Steve Ackerley for their invaluable help in devising and building the bender elements. The research was made possible through funding from the Engineering and Physical Sciences Research Council's (EPSRC's) Cooperation Awards in Science and Engineering (CASE) in collaboration with Ove Arup and Partners.

References

 

DC FieldValueLanguage
dc.contributor.authorSorensen, KKen_HK
dc.contributor.authorBaudet, BAen_HK
dc.contributor.authorSimpson, Ben_HK
dc.date.accessioned2011-08-26T14:21:35Z-
dc.date.available2011-08-26T14:21:35Z-
dc.date.issued2010en_HK
dc.identifier.citationGeotechnique, 2010, v. 60 n. 10, p. 751-763en_HK
dc.identifier.issn0016-8505en_HK
dc.identifier.urihttp://hdl.handle.net/10722/137228-
dc.description.abstractThis paper attempts to bridge the gap between the wellknown characteristics of strain rate-independent elastic stiffness and of the time-dependent behaviour of clays at large strains. Effects of acceleration, strain rate and ageing are examined in the very small to small strain region, using results from tests on reconstituted London Clay and kaolin. Static measurements of the shear modulus at small strains, using local instrumentation, indicate that the shear modulus is rate-independent when the soil is subjected to elastic deformations only. Most often, in practice, soil specimens are left to rest between the compression and shearing stages, until deformations associated with creep become negligible. The testing strain rate imposed upon shearing induces a temporary acceleration of strains, which results in very high measured stiffnesses. Test data show, however, that when the shearing axial strain rate is of the same order of magnitude as that measured at the end of the compression/creep stage, the remaining plastic creep strains influence the measured stiffness, which is then measured to be comparatively low. Test data also seem to show that temporary strain acceleration may hide effects of recent stress path rotation. Additionally, bender element tests were performed during isotropic compression tests with changes in stress rate and creep stages. The data indicate that the strain rate affects the value of the dynamic shear modulus of the soil. It is suggested that the increase in dynamic shear modulus during short-term creep is caused by mechanisms linked to the gradual decrease in strain rate during creep, but further investigation would be needed to clarify which physical mechanisms. A new method to account for strain rate in evaluating the dynamic shear modulus of normally consolidated reconstituted clays is finally proposed.en_HK
dc.languageengen_US
dc.publisherThomas Telford (ICE Publishing). The Journal's web site is located at http://www.geotechnique-ice.comen_HK
dc.relation.ispartofGeotechniqueen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsPermission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees-
dc.subjectClaysen_HK
dc.subjectCreepen_HK
dc.subjectDynamicsen_HK
dc.subjectLaboratory testsen_HK
dc.subjectStiffnessen_HK
dc.subjectTime dependenceen_HK
dc.titleInfluence of strain rate and acceleration on the behaviour of reconstituted clays at small strainsen_HK
dc.typeArticleen_HK
dc.identifier.emailBaudet, BA:baudet@hku.hken_HK
dc.identifier.authorityBaudet, BA=rp01303en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1680/geot.07.D.147en_HK
dc.identifier.scopuseid_2-s2.0-79551582069en_HK
dc.identifier.hkuros190256en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-79551582069&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume60en_HK
dc.identifier.issue10en_HK
dc.identifier.spage751en_HK
dc.identifier.epage763en_HK
dc.identifier.isiWOS:000281708100002-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridSorensen, KK=36994189400en_HK
dc.identifier.scopusauthoridBaudet, BA=15841467600en_HK
dc.identifier.scopusauthoridSimpson, B=7102222020en_HK

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