Mechanical Behaviors of Hydrate-Bearing Sediment with Different Cementation Spatial Distributions: Insight from Pore Scale

Unlike the conceptual models based on idealistic assumptions, the natural hydrate spatial distribution in sediments is multitype and presents different coalescence degrees, which could greatly influence its geomechanical behavior. In this study, we present pore-scale triaxial test results for hydrate-bearing sediments with different hydrate spatial distributions for the first time. The results show that both specimens exhibit strain-softening, and the specimen in which the hydrate present a dispersed distribution yields later and shows a larger peak strength and weaker strain-softening. The localized deformation of the specimen in which the hydrates present a dispersed distribution develops slower, and the shear band is steeper and thinner. During the shearing process, the cementation failure in the specimen which the hydrate present a dispersed distribution develops faster. However, the changing rate of the pore space characteristic seems to not be affected by the hydrate spatial distribution. Moreover, the specimen in which the hydrate present a dispersed distribution has a larger hydrate-sand interfacial area. Along with the axial loading, the hydrate-sand interfacial area would increase rapidly and even straighten. Further loading would lead to the complete failure of the hydrate-cemented structure, which would lead to the slowing of the increase in the hydrate-sand interfacial area.