Cyclic Characterisation of Low-to-Medium Density Chalk for Offshore Driven Pile DesignShow others and affiliations
2023 (English)Conference paper, Published paper (Refereed)
Sustainable development
00. Sustainable Development
Abstract [en]
Project-specific advanced laboratory testing is employed increasingly frequently in site investigations for major offshore projects. Such testing needs to focus on characterising properties under in-situ conditions, while also catering for the effects of foundation installation and subsequent service conditions, including cyclic loading. Low-to-medium density chalk, a variable soft biomicrite, can be de-structured to soft paste under dynamic percussion or large-strain repetitive shearing, posing significant challenges and uncertainties for driven pile design. This paper draws on key outcomes from undrained cyclic triaxial test programmes on both intact chalk and dynamically de-structured (putty) chalk. The cyclic response of intact chalk resembles the fatigue behaviour of hard rocks and develops little sign of damage before sharp pore pressure reductions and brittle collapse occurs. In contrast, fully de-structured chalk develops both contractive and dilative phases, as seen with silts. The associated effective stress reductions vary systematically with the number of cycles and cyclic stress ratio. A laboratory-based global axial cyclic predictive method is proposed from the experiments and employed to predict the outcomes of field axial cyclic loading pile tests. The research provides then basis for robust cyclic design guidance for piles driven in low-to-medium density chalk.
Place, publisher, year, edition, pages
2023.
National Category
Geotechnical Engineering
Identifiers
URN: urn:nbn:se:hj:diva-62777OAI: oai:DiVA.org:hj-62777DiVA, id: diva2:1807479
Conference
9th International SUT OSIG Conference “Innovative Geotechnologies for Energy Transition”, London, UK, 12-14 September 2023
2023-10-262023-10-262023-10-26Bibliographically approved