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

Abstract

Approximately 90% of gas hydrates are buried in fine-grained sediments, especially in the South China Sea. The potential instability of fine-grained sediments induced by hydrate dissociation requires investigation of the shear strength and pore pressure response of sediments during hydrate recovery. To date, most studies have focused on the undrained mechanical behavior of gas hydrate–bearing sand or gas hydrate–free clay — few studies have examined gas hydrate–bearing fine-grained sediments. Because of the low-permeability and water-saturated characteristics of the sediments in the South China Sea, a series of undrained triaxial shear tests were performed on water-saturated methane hydrate-bearing clayey–silty sediments in this area. The experimental 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. Cohesion in the Mohr–Coulomb model increases with the increase in hydrate saturation, while the internal friction angle in the Mohr–Coulomb model has little dependence on the hydrate saturation.