Predicting deformation of MHBS during hydrate dissociation using a state-dependent critical state model

Methane Hydrate-Bearing Sand (MHBS) is a natural soil deposit containing methane hydrate in its pores, which occurs in abundance in deep water marine sediments and permafrost regions. Submarine landslides may be induced by methane hydrate extraction in deep water. Thus, it is crucial to evaluate the mechanical behaviour of MHBS during hydrate dissociation. In this paper, a recently developed state-dependent critical state model for MHBS was further extended to predict the effect of hydrate dissociation on volume change and axial deformation of MHBS. In the formulation, the volume change of MHBS was derived as a combined action of the change in stress, hydrate saturation and temperature. However, the axial deformation is only affected by the change in stress and hydrate saturation. The proposed model was used to predict the laboratory hydrate dissociation tests induced by the thermal recovery method reported in Hyodo et al. (2013). It is found that despite some discrepancies the model predictions can capture some key deformation features of MHBS during hydrate dissociation. In particular, shear failure of MHBS can be predicted for specimen subjected to a high shear stress level.