Undrained shear strength determination and correlations on Søvind Marl

Gitte Lyng Grønbech, Benjaminn Nordahl Nielsen

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Abstract

Undrained shear strength on Søvind Marl is found through undrained, volume constant, triaxial testing and is compared to field vane shear strength. Søvind Marl is extremely plastic and highly fissured Eocene clay found throughout Denmark. The fissured structure of Søvind Marl has an influence on both the preconsolidation and the undrained shear strength. Two apparent values of the preconsolidation stresses can be determined due to the fissured structure (Grønbech et al. 2015) which also considerably decreases the undrained shear strength.

Determination of shear strength of fissured clay is done through field testing or triaxial testing. Christensen and Hansen (1959) tested fissured Danish Oligocene clay and found the undrained shear strength, Su, be approximately 1/3 of the measured field vane shear strength, cfv. This correlation has since been used in Danish geotechnical practice with little to no further validation through modern triaxial test.

The measured undrained shear strength is normalized using SHANSEP. The strengths are compared to the measured field vane shear strength in order to determine μ (μ=Su⁄cfv ). The undrained shear strength is found to be increasing with increasing stresses up to a strength of approximately 450 kPa at a stress level corresponding to the lower limit of the preconsolidation stresses. The field vane shear strength is found to reach values of more than 1000 kPa. The ratio between the undrained shear strength and field vane shear strength was confirmed to be approximately 0.3 on Søvind Marl regardless of the stress level.
Original languageEnglish
Title of host publicationNGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík
Number of pages10
Place of PublicationReykjavík
PublisherThe Icelandic Geotechnical Society
Publication date2016
Pages431-440
ISBN (Electronic)978-9935-24-002-6
Publication statusPublished - 2016
EventThe 17th Nordic Geotechnical Meeting - Reykjavik, Iceland
Duration: 25 May 201628 May 2016
Conference number: 17

Conference

ConferenceThe 17th Nordic Geotechnical Meeting
Number17
CountryIceland
CityReykjavik
Period25/05/201628/05/2016

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shear strength
vanes
clays
Denmark
plastics

Keywords

  • Undrained shear strength
  • Fissured clay
  • SHANSEP
  • Plastic clay
  • Field vane shear strength

Cite this

Grønbech, G. L., & Nielsen, B. N. (2016). Undrained shear strength determination and correlations on Søvind Marl. In NGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík (pp. 431-440). Reykjavík: The Icelandic Geotechnical Society.
Grønbech, Gitte Lyng ; Nielsen, Benjaminn Nordahl. / Undrained shear strength determination and correlations on Søvind Marl. NGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík. Reykjavík : The Icelandic Geotechnical Society, 2016. pp. 431-440
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Grønbech, GL & Nielsen, BN 2016, Undrained shear strength determination and correlations on Søvind Marl. in NGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík. The Icelandic Geotechnical Society, Reykjavík, pp. 431-440, The 17th Nordic Geotechnical Meeting, Reykjavik, Iceland, 25/05/2016.

Undrained shear strength determination and correlations on Søvind Marl. / Grønbech, Gitte Lyng; Nielsen, Benjaminn Nordahl.

NGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík. Reykjavík : The Icelandic Geotechnical Society, 2016. p. 431-440.

Research output: Contribution to book/anthology/report/conference proceedingArticle in proceedingResearchpeer-review

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AB - Undrained shear strength on Søvind Marl is found through undrained, volume constant, triaxial testing and is compared to field vane shear strength. Søvind Marl is extremely plastic and highly fissured Eocene clay found throughout Denmark. The fissured structure of Søvind Marl has an influence on both the preconsolidation and the undrained shear strength. Two apparent values of the preconsolidation stresses can be determined due to the fissured structure (Grønbech et al. 2015) which also considerably decreases the undrained shear strength.Determination of shear strength of fissured clay is done through field testing or triaxial testing. Christensen and Hansen (1959) tested fissured Danish Oligocene clay and found the undrained shear strength, Su, be approximately 1/3 of the measured field vane shear strength, cfv. This correlation has since been used in Danish geotechnical practice with little to no further validation through modern triaxial test.The measured undrained shear strength is normalized using SHANSEP. The strengths are compared to the measured field vane shear strength in order to determine μ (μ=Su⁄cfv ). The undrained shear strength is found to be increasing with increasing stresses up to a strength of approximately 450 kPa at a stress level corresponding to the lower limit of the preconsolidation stresses. The field vane shear strength is found to reach values of more than 1000 kPa. The ratio between the undrained shear strength and field vane shear strength was confirmed to be approximately 0.3 on Søvind Marl regardless of the stress level.

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KW - Fissured clay

KW - SHANSEP

KW - Plastic clay

KW - Field vane shear strength

KW - Undrained shear strength

KW - Fissured clay

KW - SHANSEP

KW - Plastic clay

KW - Field vane shear strength

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M3 - Article in proceeding

SP - 431

EP - 440

BT - NGM 2016 Proceedings

PB - The Icelandic Geotechnical Society

CY - Reykjavík

ER -

Grønbech GL, Nielsen BN. Undrained shear strength determination and correlations on Søvind Marl. In NGM 2016 Proceedings : Proceedings of the 17th Nordic Geotechnical Meeting, Reykjavík. Reykjavík: The Icelandic Geotechnical Society. 2016. p. 431-440