Geotechnical characterization of marine sediments in the Ulleung Basin, East Sea

Changho Lee, Tae Sup Yun, Jong Sub Lee*, Jang Jun Bahk, Juan Carlos Santamarina

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

The geotechnical characteristics of Ulleung Basin sediments are explored using depressurized samples obtained at 2100. m water depth and 110. m below the sea floor. Geotechnical index tests, X-ray diffraction, and SEM images were obtained to identify the governing sediment parameters, chemical composition and mineralogy. We use an instrumented multi-sensor oedometer cell to determine the small-strain stiffness, zero-lateral strain compressibility and electromagnetic properties, and a triaxial device to measure shear strength. SEM images show a sediment structure dominated by microfossils, with some clay minerals that include kaolinite, illite, and chlorite. The preponderant presence of microfossils determines the high porosity of these sediments, defines their microstructure, and governs all macroscale properties. The shear wave velocity increases as the vertical effective stress increases; on the other hand, porosity, permittivity, electrical conductivity, and hydraulic conductivity decrease with increasing confinement. All these parameters exhibit a bi-linear response with effective vertical stress due to the crushable nature of microfossils. Well-established empirical correlations used to evaluate engineering parameters do not apply for these diatomaceous sediments which exhibit higher compressibility than anticipated based on correlations with index properties. Settlements will be particularly important if gas production is attempted using depressurization because this approach will cause both hydrate dissociation and increase in effective stress.

Original languageEnglish (US)
Pages (from-to)151-158
Number of pages8
JournalEngineering Geology
Volume117
Issue number1-2
DOIs
StatePublished - Jan 10 2011

Keywords

  • Compressibility
  • Diatomaceous sediment
  • Electrical conductivity
  • Hydrate-bearing sediments
  • Microstructure
  • Mineralogy
  • Permittivity
  • Stiffness

ASJC Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

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