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

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 tha...

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Bibliographic Details
Published in:Géotechnique 2019-11, Vol.69 (11), p.959-970
Main Authors: Colreavy, Cathal, O'Loughlin, Conleth D., Bishop, Daniel T., Randolph, MARK F.
Format: Article
Language:English
Subjects:
Beds (geology)
Biofilms
Biological effects
Biology
Cations
Chemistry
Clay
Crosslinking
Fossils
Organic chemistry
Penetrometers
Pore water
Sediment
Sediments
Soil
Soil biology
Soil strength
Soil water
Soils
Strength
Water chemistry
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Summary: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.
ISSN:0016-8505
1751-7656
DOI:10.1680/jgeot.16.P.308