Preliminary Experimental Investigation on the Geomechanical Behaviour of Hydrate-Bearing Fine-grained Sediments

ABSTRACT: The existence of gas hydrate within deep marine sediments influences the geomechanical properties of the host sediment. As such, dissociation of the hydrate, through ongoing climate change or through future production of the hydrate, may pose a significant risk to submarine slope stability. Although extensive research has been conducted on hydrate-bearing sands, very limited studies on geomechanical behaviour of gas hydrate-bearing fine-grained soils have been reported in the literature. This paper presents the initial results of a study to investigate the impact of hydrate veins on the K0 compression of hydrate-bearing fine grained sediments. An experimental investigation was carried out using fine-grained soil specimens with cylindrical carbon dioxide hydrate-bearing sand cores to mimic natural hydrate vein-bearing fine-grained sediment. After formation of the hydrate, K0 compression tests were carried out to explore differences in axial deformation of the specimens as a function of applied vertical stresses. Test results indicate that brittle yielding occurred during K0 compressions due to the breakage of the bond between the hydrate and the host grains as well as the high content of stiff hydrate. The hydrate-bearing fine-grained specimen is capable of withstanding much greater axial loads than the baseline specimen. Before yielding, the axial load was primarily carried through the hydrate vein, while after yielding, the specimen behaviour approached that for the baseline case.