Effects of fine content and water saturation on the mechanical properties of hydrate-bearing fine-grained soils

The gas hydrate reserves in the Shenhu area of the South China Sea hold significant commercial value. However, the predominance of fine-grained clayey silt in this region poses severe challenges to safe exploitation, as the mechanical response of these sediments under dissociation conditions remains poorly understood. To address this, hydrate-bearing soil specimens were prepared using tetrahydrofuran (THF) to replicate the particle size distribution of Shenhu sediments. A series of triaxial shear tests was conducted to evaluate the effects of fines content and water saturation on shear strength and deformation characteristics. Experimental results indicate that hydrates significantly enhance the cohesion of fine-grained soils, although this strengthening effect diminishes with increasing fines content. With increasing fines content, the strain softening behavior of hydrate-bearing specimens gradually attenuates. At the same time, stiffness and dilatancy decrease, while cohesion and peak strength initially decrease, then increase. Furthermore, increasing water saturation from 0% to 40% resulted in a 76.2% reduction in cohesion, accompanied by a decline in peak strength and stiffness. Conversely, both fines content and water saturation were found to have a negligible impact on the internal friction angle. These findings offer a theoretical basis for the design and safe execution of hydrate exploitation projects.