Shear strength and pore pressure characteristics of methane hydrate-bearing soil under undrained condition |
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| Affiliation: | 1. Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering, College of Civil Engineering and Architecture, Guilin University of Technology, Guilin, Guangxi, 541004, PR China;2. School of Architecture and Transportation Engineering, Guilin University of Electronic Technology, Guilin, Guangxi, 541004, PR China;1. Faculty of Engineering, China University of Geosciences, Wuhan, 430074, China;2. National Center for International Research on Deep Earth Drilling and Resource Development, China University of Geosciences (Wuhan), Wuhan, 430074, China;3. Laboratory for Marine Mineral Resource, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao, 266071, China;4. Key Laboratory of Gas Hydrate, Ministry of Natural Resource, Qingdao Institute of Marine Geology, Qingdao, 266071, China;5. Graduate School of Science and Technology for Innovation, Yamaguchi University, Ube, Yamaguchi, 7550097, Japan;1. Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian, 116024, PR China;2. State Key Laboratory of Natural Gas Hydrate, Beijing, 100028, PR China;1. Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering, College of Civil Engineering and Architecture, Guilin University of Technology, Guilin, Guangxi, 541004, PR China;2. School of Architecture and Transportation Engineering, Guilin University of Electronic Technology, Guilin, Guangxi, 541004, PR China |
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| Abstract: | Hydrate exploitation requires a deep understanding on the mechanical behavior of methane hydrate-bearing sediment (MHBS). Due to the low permeability of overlying strata, partial MHBS likely exhibit failure behavior under undrained condition. Therefore, it is essential to understand the undrained shear strength and excess pore pressure behavior of MHBS for facilitating the evaluation of the stability of hydrate-bearing layer during methane hydrate recovery. This study conducted several undrained triaxial compression and hydrate dissociation tests on methane hydrate-bearing sand specimen to analyze the shear strength and excess pore pressure characteristics of MHBS under undrained condition. The experimental result shows that hydrate saturation and initial effective confining pressure significantly affect the undrained mechanical behavior of MHBS. Hydrate saturation increases the shear strength and negative excess pore pressure. High initial effective confining pressure also enhances the shear strength but suppressed the negative excess pore pressure. Hydrate saturation has a minimal effect on the undrained internal friction angle but remarkably enhances the undrained cohesion. The effective internal friction angle and cohesion exhibits an increase with the increase in hydrate saturation. Notably, completely different from the common soil, the effective undrained strength indexes are not equivalent to the drained strength indexes for MHBS, which should be careful in evaluating the stability of methane hydrate-bearing layer. In addition, the hydrate dissociation test by thermal stimulation method concludes that hydrate dissociation induces the positive excess pore pressure, axial compression, and volume expansion under undrained condition. The large deviatoric stress enhances volume expansion of MHBS but hinders the generation in excess pore pressure during hydrate dissociation. These findings significantly contribute to the safe exploitation process of methane hydrate. |
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| Keywords: | Methane hydrate-bearing soil Undrained condition Pore pressure Shear strength Hydrate dissociation |
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