Characterising chalk-concrete interfaces for offshore renewable energy foundations

A. Ziogos, M. J. Brown, A. Ivanovic, N. Morgan

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Abstract

Deployment of renewable energy foundations, be it piles or gravity based structures, may come into contact with chalk in southern UK waters and in other parts of European offshore and nearshore deployment. To aid more appropriate design it is useful to understand the interface shear strength between the foundation and the underlying rock where this is exposed at surface or where the foundation penetrates. In this paper, the interface shear strength between chalk and unbonded concrete is investigated for constant normal stress conditions over a range of normal stresses using tilt table and specialised interface shear testing apparatus. The results show that the interface strength of chalk is significantly influenced by the normal stress used during testing where at lower stresses the interface strength exceeds the basic friction angle determined for a chalk-chalk interface and degradation of the interface strength below the basic friction angle occurs when normal stresses exceed 73% of the tensile strength of the chalk material. This degradation is more severe at small displacements than previously observed for chalk-steel interfaces. At low normal stresses and displacements, the shear strength of the chalkconcrete interface can be represented by an alpha type approach related to the chalk unconfined compressive strength as previously developed for higher strength rocks.

Original languageEnglish
Title of host publicationEngineering in Chalk
Subtitle of host publicationProceedings of the Chalk 2018 Conference
EditorsJ. A. Lawrence, M. Preene, U. L. Lawrence, R. Buckley
Place of PublicationLondon
PublisherICE Publishing
Pages521-527
Number of pages7
ISBN (Electronic)9780727764089
ISBN (Print)9780727764072
DOIs
Publication statusPublished - 2018
EventEngineering in Chalk 2018 International Conference - Imperial College London, London, United Kingdom
Duration: 17 Sep 201819 Sep 2018
https://www.chalk2018.org/about/committees

Conference

ConferenceEngineering in Chalk 2018 International Conference
CountryUnited Kingdom
CityLondon
Period17/09/1819/09/18
Internet address

Fingerprint

Concretes
Shear strength
Rocks
Friction
Degradation
Testing
Compressive strength
Piles
Gravitation
Tensile strength
Steel
Water

Keywords

  • Chalk
  • interface
  • Shear
  • Renewable energy
  • marine energy
  • concrete

Cite this

Ziogos, A., Brown, M. J., Ivanovic, A., & Morgan, N. (2018). Characterising chalk-concrete interfaces for offshore renewable energy foundations. In J. A. Lawrence, M. Preene, U. L. Lawrence, & R. Buckley (Eds.), Engineering in Chalk: Proceedings of the Chalk 2018 Conference (pp. 521-527). London: ICE Publishing. https://doi.org/10.1680/eiccf.64072.521
Ziogos, A. ; Brown, M. J. ; Ivanovic, A. ; Morgan, N. / Characterising chalk-concrete interfaces for offshore renewable energy foundations. Engineering in Chalk: Proceedings of the Chalk 2018 Conference. editor / J. A. Lawrence ; M. Preene ; U. L. Lawrence ; R. Buckley. London : ICE Publishing, 2018. pp. 521-527
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Ziogos, A, Brown, MJ, Ivanovic, A & Morgan, N 2018, Characterising chalk-concrete interfaces for offshore renewable energy foundations. in JA Lawrence, M Preene, UL Lawrence & R Buckley (eds), Engineering in Chalk: Proceedings of the Chalk 2018 Conference. ICE Publishing, London, pp. 521-527, Engineering in Chalk 2018 International Conference, London, United Kingdom, 17/09/18. https://doi.org/10.1680/eiccf.64072.521

Characterising chalk-concrete interfaces for offshore renewable energy foundations. / Ziogos, A.; Brown, M. J.; Ivanovic, A.; Morgan, N.

Engineering in Chalk: Proceedings of the Chalk 2018 Conference. ed. / J. A. Lawrence; M. Preene; U. L. Lawrence; R. Buckley. London : ICE Publishing, 2018. p. 521-527.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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N2 - Deployment of renewable energy foundations, be it piles or gravity based structures, may come into contact with chalk in southern UK waters and in other parts of European offshore and nearshore deployment. To aid more appropriate design it is useful to understand the interface shear strength between the foundation and the underlying rock where this is exposed at surface or where the foundation penetrates. In this paper, the interface shear strength between chalk and unbonded concrete is investigated for constant normal stress conditions over a range of normal stresses using tilt table and specialised interface shear testing apparatus. The results show that the interface strength of chalk is significantly influenced by the normal stress used during testing where at lower stresses the interface strength exceeds the basic friction angle determined for a chalk-chalk interface and degradation of the interface strength below the basic friction angle occurs when normal stresses exceed 73% of the tensile strength of the chalk material. This degradation is more severe at small displacements than previously observed for chalk-steel interfaces. At low normal stresses and displacements, the shear strength of the chalkconcrete interface can be represented by an alpha type approach related to the chalk unconfined compressive strength as previously developed for higher strength rocks.

AB - Deployment of renewable energy foundations, be it piles or gravity based structures, may come into contact with chalk in southern UK waters and in other parts of European offshore and nearshore deployment. To aid more appropriate design it is useful to understand the interface shear strength between the foundation and the underlying rock where this is exposed at surface or where the foundation penetrates. In this paper, the interface shear strength between chalk and unbonded concrete is investigated for constant normal stress conditions over a range of normal stresses using tilt table and specialised interface shear testing apparatus. The results show that the interface strength of chalk is significantly influenced by the normal stress used during testing where at lower stresses the interface strength exceeds the basic friction angle determined for a chalk-chalk interface and degradation of the interface strength below the basic friction angle occurs when normal stresses exceed 73% of the tensile strength of the chalk material. This degradation is more severe at small displacements than previously observed for chalk-steel interfaces. At low normal stresses and displacements, the shear strength of the chalkconcrete interface can be represented by an alpha type approach related to the chalk unconfined compressive strength as previously developed for higher strength rocks.

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Ziogos A, Brown MJ, Ivanovic A, Morgan N. Characterising chalk-concrete interfaces for offshore renewable energy foundations. In Lawrence JA, Preene M, Lawrence UL, Buckley R, editors, Engineering in Chalk: Proceedings of the Chalk 2018 Conference. London: ICE Publishing. 2018. p. 521-527 https://doi.org/10.1680/eiccf.64072.521