Undrained triaxial tests on water-saturated methane hydrate-bearing clayey-silty sediments of the South China Sea

Approximately 90% of gas hydrates are buried in fine-grained sediments on earth, especially in the South China Sea. The potential instability of the fine-grained sediments induced by hydrate dissociation requires us to investigate the shear strength and pore pressure response of the sediments during the hydrate recovery. To date, most of studies focused on the undrained mechanical behavior of gas hydrate-bearing sand or gas hydrate-free clay, and few studies examined gas hydrate-bearing fine-grained sediments. According to the low-permeability and water-saturated characteristics of the sediments in the South China Sea, we performed a series of undrained triaxial shear tests on water-saturated methane hydrate-bearing clayey-silty sediments in this area. The experiment results show that the failure strength of methane hydrate-bearing sediments (MHBSs) increases with the increase in hydrate saturation and initial effective mean stress. The excess pore water pressure of MHBSs remains positive during shear. The cohesion in Mohr-Coulomb model increases with the increase in hydrate saturation, while the internal friction angle in Mohr-Coulomb model has little dependence on the hydrate saturation.