Dynamic strength characteristics of methane hydrate-bearing sediments under seismic load

• The rate of sediment deformation increases gradually under seismic load.
• The failure number of cycles increases linearly with decreasing dynamic strength.
• The dynamic strength was affected by confining pressure, temperature and porosity.
• Dynamic strength decreases by reduction of cohesion and internal friction angle.

The research on the mechanical properties of hydrate-bearing sediments has attracted great attention to ensure the safety production of methane from hydrates. To study the dynamic strength characteristics of methane hydrate-bearing sediments under seismic load, a series of dynamic triaxial tests was performed on artificial methane hydrate-bearing sediments under various conditions, with confining pressures at 2, 1 and 0.5 MPa; temperatures at −5, −3 and −1 °C; and porosities at 40% and 80%. The dynamic stress-strain behavior and curves of dynamic strain versus number of cycles were obtained and analyzed. The dynamic strength curves showed that the failure number of cycles was significantly affected by the dynamic stress amplitude. The dynamic strength of methane hydrate-bearing sediments increased with increasing confining pressure and decreased with increasing temperature and porosity. Based on the Mohr–Coulomb strength criterion, Mohr's circles and strength envelopes were drawn, and the mechanism of the influence of temperature and porosity on the dynamic strength of the sediments was revealed. The results indicated that increasing temperature would reduce the dynamic strength by reducing the soil cohesion and internal friction angle, while increasing porosity would reduce the dynamic strength mainly by reducing the soil internal friction angle.