Abstract: Triaxial shear tests were conducted on self-prepared hydrate-bearing sediments to obtain the influences of effective confining pressure and saturation on the strength and rigidness of hydrate-bearing sediments. The test specimens were made from artificial clayey fine sand in reference to the particle size distribution of sediment in the north part of South China Sea. CO₂ hydrate-bearing sediments with different saturations were prepared by a self-developed triaxial test machine, and the triaxial shear tests were carried out under the effective confining pressure of 1 MPa, 2 MPa, and 4 MPa. As confining pressure changes automatically with gas pressure, the effective confining pressure remained unchanged during the formation of hydrate when gas was consumed. The experimental results reveal that the initial elastic modulus increased with the rising of hydrate saturation, while independent of the effective confining pressure. The initial Poisson ratio decreased with the increase of effective confining pressure while grew with the rising of hydrate saturation. The strength index cohesive force increased with the increase of hydrate saturation, while the internal friction angle was independent of hydrate saturation. In addition, the nonlinear elastic constitutive model for hydrate-bearing sediment was established by introducing a parameter hydrate saturation based on Duncan-Chang’s model, and the proposed model was validated by test data.

Key words: hydrate-bearing sediments, clayey sand, triaxial test, mechanical behavior, constitutive model