Failure mechanisms in cemented hydrate-bearing sands

A significant portion of our knowledge on gas hydrate-bearing sands comes from experimental results on laboratory-synthesized specimens. The failure mechanics are often interpreted using components of the stress-strain curves, which capture the specimen's global (large-scale) response to shear. In this paper, we postulate on the microscale mechanics, which lead to a variety of interesting global behaviors. Two mechanisms of failure during shear are postulated: one involves debonding of the hydrate particle from the soil solid, and the other involves crushing or breakage through the hydrate itself. Both modes of failure lead to similar peak strengths, which arise from both friction and apparent cohesion induced by the hydrate bonding; however, the differences observed in postpeak softening may be attributed to the different failure mechanisms. Global specimen responses such as sudden strength loss, occurrence of double shear banding, and differences in postpeak behavior are manifestations of the microscale hydrate sand interactions.