Triaxial Compression Strength of Methane Hydrate-Bearing Sediments
Date
2013-09-13
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Abstract
Hydrate-bearing sediments are characterized as soils in which the pore space is partially or fully occupied by ice-like crystalline solid consisting of hydrogen bonded water lattices encapsulating guest gas molecules, mostly methane in natural environments. These sediments are found along marine continental margins and in permafrost regions. The main focus of this thesis is to investigate the behaviour of hydrate-bearing sediments subject to triaxial compression. The work presented includes (1) an investigation into the formation process dependency of hydrate growth habit, spatial distribution, and saturation (the key deterministic factors of the physical behaviour), (2) a novel formation methodology to isolate the effects of formation habit from those of spatial variation in hydrate distribution, (3) an investigation into the accurate estimation of hydrate saturation, (4) and a comprehensive series of tests to investigate the initial effective confining stress and hydrate saturation dependent stress-strain behaviour, strength, and stiffness, (5) a comparison of present results with previous work published in literature to investigate the differences in strength/stiffness behaviour between different formation habits. The results of the study reveal that the stress-strain behaviour is affected by hydrate added cohesion (or cementation), the failure strength at low saturations is controlled by frictional resistance at mineral grain contacts, the failure strength at high saturations is determined predominantly by hydrate-mineral bonding strength or intact hydrate breakage strength while the residual strength is determined by the hydrate saturation, stiffness is controlled predominantly by formation habit while hydrate saturation acts as a factor of secondary importance, and the effects of initial effective confinement on the strength/stiffness behaviour is significant only at low hydrate saturations. Additionally, an increased dilative tendency, reflected in strongly negative pore pressure development was observed in the hydrate-bearing specimens under constant mass shearing. Comparison of our results of the experimental program with theoretical predictions generates a good match, which indicates that theoretical modeling of the strength gain due to the presence of gas hydrates is possible. The knowledge generated in this research is essential in evaluating the potential risks associated with drilling and methane production, reservoir subsidence, and dissociation induced submarine slope instability.
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Civil, Petroleum, Geotechnology
Citation
Jaysinghe, A. (2013). Triaxial Compression Strength of Methane Hydrate-Bearing Sediments (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/28526