Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture

An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid...

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Bibliographic Details
Published in:Journal of Geophysical Research 2011-04, Vol.116 (B4), p.n/a, Article B04207
Main Authors: Algar, C. K., Boudreau, B. P., Barry, M. A.
Format: Article
Language:English
Subjects:
Biological oceanography
Bubbles
Chemical oceanography
Cohesive sediments
fracture
Gas hydrates
Geophysics
Hydrates
Hydrology
Marine geology
methane
Physical properties
Rocks
viscoelasticity
Wetlands
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Summary:An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles in soft sediments, and this paper presents a new model for gas bubble rise in soft, fine‐grained, cohesive sediments. Bubbles in such sediments are essentially “dry” (little if any free water) and grow through a process of elastic expansion and fracture that can be described using the principles of linear elastic fracture mechanics, which assume the existence of a spectrum of flaws within the sediment fabric. By extending this theory, we predict that bubbles initially rise by preferential propagation of a fracture in a (sub) vertical direction. We present a criterion for initial bubble rise. Once rise is initiated, the speed of rise is controlled by the viscoelastic response of the sediments to stress. Using this new bubble rise model, we estimate rise velocities to be of the order of centimeters per second. We again show that capillary pressure plays no substantive role in controlling bubble growth or rise. Key Points Gas bubbles in cohesive sediments rise by a process of viscoelastic fracture Rise occurs when the long axis of the bubble reaches a critical length The time scale of viscoelastic response most likely controls the rise velocity
ISSN:0148-0227
2169-9313
2156-2202
2169-9356
DOI:10.1029/2010JB008133