Mechanical behaviours of gas-hydrate-bearing clayey sediments of the South China Sea

To investigate the stability of gas-hydrate-bearing sediments under the seabed, many researchers have studied their mechanical behaviours, including strength and deformation characteristics. However, most researchers have focused on hydrate-bearing sand, and there are few publications on hydrate-bearing clay. In this paper, a series of experiments were conducted using remoulded gas-hydrate-bearing sediments drilled from the South China Sea whose host sediments primarily consisted of clay. The particle size, specific surface area, pore size distribution and scanning electron microscopy images of the host sediments were analysed, and triaxial tests were conducted to study their mechanical behaviours under different hydrate saturations and effective confining pressures. The results indicated that strength and stiffness increase with increasing hydrate saturation under the same effective confining pressure. The effective confining pressure could enhance the strength and stiffness at nearly the same hydrate saturation. The analysis of the Mohr circles and failure envelopes of the hydrate-bearing sediments under four different hydrate saturations revealed that the cohesion and internal friction angle increase with an increase in hydrate saturation.