The stress and strain dependent response of THF hydrate

Abstract

Large volumes of methane gas hydrate reside within fine-grained marine sediments on continental slopes within the Arctic region, where hydrate exists as fracture filling veins that may hinder normal consolidation processes during ongoing burial. Hydrate dissociation due to anthropogenic induced climate change, which is magnified in the Artic, may lead to significant weakening of the sediment triggering slope instabilities. However, the potential response of hydrate veins under axial loading is poorly understood. To gain better insights a series of uniaxial compression tests, under different stress and strain conditions, were conducted on cylindrical tetrahydrofuran (THF) hydrate specimens with different slenderness ratios. Results highlight the strain rate dependent behavior of the THF hydrate with compressive strength reducing with reducing strain rate. Specimens with high slenderness ratios under high strain rates failed predominantly from spontaneous brittle buckling of the specimen, while for low slenderness ratio specimens, at low strain rates, hydrate behavior is more ductile resulting in lower peak stresses but higher residual stresses. Hydrate under constant stresses exhibited extensive plastic deformation as axial stresses approached failure conditions, with low slenderness ratios showing extensive cracking and shear dislocations, while those high slenderness ratios experienced large out-of-plane deformations. The stress-strain response of the hydrate suggests that at shallow burial depths such as that on the Arctic continental slope where climate change will have the greatest impact, hydrate veins will inhibit sediment consolidation. However, at greater burial stresses the plastic deformation of the hydrate veins may not provide significant impediment to sediment consolidation. Further research is required to characterize the impact of the sediment matrix on hydrate behavior.