A new strength criterion and constitutive model of gas hydrate-bearing sediments under high confining pressures

• Mechanical properties of gas hydrate-bearing sediments were studied in this paper.
• The strength decreases with increasing confining pressure when pressure ≥5 MPa.
• A new strength criterion is proposed to reflect the failure load.
• Duncan–Chang model is used to describe the deformation behavior.
• The results predicted by the model agree well with the experimental data.

Mechanical properties of gas hydrate-bearing sediments are important for the safe production of natural gas from hydrate reservoirs, as well as conventional oil or gas beneath the gas hydrate bearing sediments. In order to determine the failure load and describe the deformation behavior of gas hydrate-bearing sediments in deepwater regions, a series of triaxial compression tests on synthetic gas hydrate-bearing sediment cores were conducted under high confining pressures and a temperature of −10 °C. The results verify that the deviator stress increases gradually with increasing axial strain and finally reaches a constant value without significant peak value. When confining pressure ≥5 MPa, the failure strength decreases with increasing confining pressure because of particle crushing and pressure melting of ice. A new strength criterion to well reflect the failure load of gas hydrate-bearing sediments under high confining pressures is proposed based on the experimental results. The Duncan–Chang model is used to describe the deformation behavior of gas hydrate-bearing sediments under various confining pressures, and it is found that the results predicted by the model agree well with the experimental data.