Effect of soil biology and pore water chemistry on a lakebed sediment

Cathal Colreavy, Conleth D. O'Loughlin, Daniel T. Bishop, Mark F. Randolph

    Research output: Contribution to journalArticle

    Abstract

    This paper attempts to explain how a normally consolidated lakebed sediment can have an undrained strength ratio of approximately unity, when the lithic component of the sediment is less than 3% by volume. The structured clay framework, coupled with sensitivity measurements of the sediment, show that the structure retains a very high strength in a remoulded state. Close examination of the sediment indicates a significant microfossil presence. When considered together with the depositional environment and local water chemistry, this suggests that the soil strength arises from a structural matrix of biofilm adhering to the clay and microfossil particles, which is enhanced by cross-linking due to the presence of multi-valent cations in the local water. Laboratory-scale piezocone, piezoball and T-bar penetrometer tests show that the strength and consolidation characteristics can be significantly altered by changes in the pore water chemistry, an observation that should be considered in geotechnical design for such soils.

    Original languageEnglish
    Pages (from-to)959-970
    Number of pages12
    JournalGeotechnique
    Volume69
    Issue number11
    DOIs
    Publication statusPublished - 1 Nov 2019

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