Abstract
Creep behaviors of methane hydrate-bearing frozen specimens are important to predict the long-term stability of the hydrate-bearing layers in Arctic and permafrost regions. In this study, a series of creep tests were conducted, and the results indicated that: (1) higher deviator stress (external load) results in larger initial strain, axial strain, and strain rate at a specific elapsed time. Under low deviator stress levels, the axial strain is not large and does not get into the tertiary creep stage in comparison with that under high deviator stress, which can be even up to 35% and can cause failure; (2) both axial strain and strain rate of methane hydrate-bearing frozen specimens increase with the enhancement of deviator stress, the decrease of confining pressure, and the decrease of temperature; (3) the specimens will be damaged rather than in stable creep stage during creeping when the deviator stress exceeds the quasi-static strength of the specimens.
Highlights
IntroductionMethane hydrate is an ice-like substance, in which methane (the main component of natural gas) is trapped within a cage structure composed of water molecules under low temperature and relatively high pressure conditions
Methane hydrate is an ice-like substance, in which methane is trapped within a cage structure composed of water molecules under low temperature and relatively high pressure conditions
The results showed that the methane hydrate-bearing sand specimen presented typical creep curves and had considerable time dependence, and the strain rate was inversely proportional to the m-th power of elapsed time and residual time at the beginning of creep test and before failure of the specimen, respectively
Summary
Methane hydrate is an ice-like substance, in which methane (the main component of natural gas) is trapped within a cage structure composed of water molecules under low temperature and relatively high pressure conditions. In view of the problems, the mechanical behaviors of methane hydrate-bearing layers should be clarified to assess the stability of the layers and the production well before methane hydrate commercial production [6]. To address this issue, a series of triaxial and plane compression tests were conducted to investigate the mechanical properties of methane hydrate-bearing sediments before, during, and after hydrate dissociation [7,8,9]. The primary mechanism of methane hydrate induced slope failure is that the dissociation of hydrate to free gas, resulting in a significant pore pressure increase and cementation loss in layers. Mountjoy et al [13]
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