Consequences of drying on the hydro-mechanical response of fibrous peats upon compression

Peats are encountered in waterlogged deltaic areas, where degradation is delayed by favourable environmental conditions. The recent increase in frequency and severity of droughts is expected to accelerate peat degradation, in turn increasing subsidence and flood risk, urging better understanding of...

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Bibliographic Details
Published in:Canadian geotechnical journal 2022-10, Vol.59 (10), p.1712-1727
Main Authors: Zhao, H.F, Jommi, C
Format: Article
Language:English
Subjects:
Compressibility
Compression
Compression tests
Computed tomography
Degradation
Desaturation
Drought
Drying
Environmental conditions
Environmental risk
Fibers
Flood risk
Geological research
Hydraulic conductivity
Hydrogeology
Mechanical analysis
Mechanical properties
Peat
Peatlands
Perturbation
Pores
Saturation
Subsidence
Tomography
Void ratio
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Summary:Peats are encountered in waterlogged deltaic areas, where degradation is delayed by favourable environmental conditions. The recent increase in frequency and severity of droughts is expected to accelerate peat degradation, in turn increasing subsidence and flood risk, urging better understanding of the response of peats to drying events. To this aim, compression tests on natural and reconstituted peat samples were performed, supported by X-ray micro-computed tomography. The peat fabric was found to be the key factor in the response to drying, with fibres playing the most significant role. Drying in peats starts affecting the macro-fabric, with an irreversible reduction in volume and disruption of the fibrous network occurring under saturated conditions until a threshold void ratio is reached, below which desaturation occurs of the intra-fibres and intra-peds pores. The first drying stage dramatically decreases the compressibility, while the hydraulic conductivity is hardly affected due to the enlargement of macropores. Secondary compressibility is affected by the peat fabric besides the organic content. The total organic content does not change substantially during drying; hence, it is not the best proxy to describe the consequences of drying on the response of fibrous peats. The fibre content can be better used to serve the aim.
ISSN:0008-3674
1208-6010
DOI:10.1139/cgj-2020-0086