Triaxial Tests of Hydrate-Bearing Clayey-Silty Sediments Under Different Hydrate Saturations and Effective Confining Pressures

It is of great significance to study the mechanical properties of hydrate-bearing sediments for safe and efficient exploitation of hydrate resources. Considering the lack of studies on clay-bearing fine-grained reservoirs, submarine clay taken from the Shenhu Sea in the South China Sea and quartz sand were used to synthesize hydrate-bearing clayey-silty sediments (HBCS). A series of consolidated-drained tests were carried out to investigate the effects of hydrate saturation, effective confining pressure, and their coupling on the mechanical properties of HBCS. The results show that with the increase in hydrate saturation and the decrease in effective confining pressure, the stress–strain curve of the HBCS shows a trend from strain hardening to strain softening. The peak strength and residual strength increase with the increase in effective confining pressure and hydrate saturation. The secant modulus E50 increases with the increase in hydrate saturation and shows an irregular change trend with the increase in effective confining pressure. The contact area between particles determines the change rule of Secant modulus E50. With the increase in hydrate saturation, the cohesion first increased rapidly and then increased slowly. The internal friction angle increases with the increase in hydrate saturation, but the increase is small. This indicates that hydrate has a great influence on the cohesion of sediments, but a small influence on the internal friction angle.