Experimental study on mechanical characteristics of gas hydrate-bearing sands containing different fines

The skeleton structure of gas hydrate-bearing sediments from ocean gas exploitation is composed of coarse grains and fines. A series of low-temperature and high-pressure triaxial drained shear tests are performed to examine the effects of fines and density on the strength and deformation properties of host sands with and without gas hydrate. The results imply that the shear strength and dilation tendency increase with a rise in fines. The rise in fines alerts hydrate morphology and distribution pattern among sand grains. The cluster of coarse grains and fines bonded by hydrate are formed in samples. The shear behavior of host sands exhibits opposite varying tendency with the increasing fines. Moreover, the stress-dilatancy relationship can be modeled using the equation adopted by the modified Cam-clay model and is dependent on hydrate saturation. At a larger hydrate saturation level, the natural samples own a higher peak friction angle and larger increasing speed with the level of gas hydrate than the gas hydrate-bearing samples synthetized in laboratory. The difference is originated from the nucleation mode and distribution pattern of hydrate mass among sand grains.