Strength behaviours of methane hydrate-bearing marine sediments in the South China Sea

Understanding the mechanical response of hydrate-bearing marine sediments (HBMSs) prior to gas production enables engineers to forecast risks associated with large-scale methane extraction from silty hydrate reservoirs in the South China Sea. To this end, this study remoulded HBMSs containing hydrate with pore-spacing or cementing morphologies and then designed a series of drained shear tests on these materials. The results show that the HBMSs containing hydrate in cementing morphology present greater strength behaviours than and similar deformation characteristics to those containing hydrate in pore-spacing morphology. The increase in effective confining pressure magnifies the enhancement effect of hydrate on the stiffness and strength of marine sediments, which is more pronounced for the hydrate in pore-spacing morphology. The cohesion of marine sediments decreases and the internal friction angle increases as the hydrate forms, while the cohesion and internal friction angle show a slight decrease when the hydrate morphology transforms from cementing to pore-spacing. The results are expected to motivate future studies of the strength behaviours of silty hydrate reservoirs. • Pore-spacing hydrate are re-formed in cores drilled from the South China Sea. • Cementing hydrate shows higher strength and similar deformation than pore-spacing. • Effective stress affects the pore-spacing effect of hydrate on marine sediments. • Cohesion of sediment reduces and internal friction angle increases as hydrates form. • Sediments with pore-spacing hydrate show lower cohesion and internal friction angle.