Analysis of the mechanical properties of methane hydrate-bearing sands with various pore pressures and confining pressures

As a kind of new clean energy, natural gas hydrate has captured headlines around the world. A full study of the mechanical properties of natural gas hydrate-bearing sediments is a prerequisite for the exploitation of hydrate reserves. In this paper, a series of consolidated-drained triaxial tests were conducted to study the mechanical properties of methane hydrate-bearing sediments under different pore pressures and effective confining pressures. The results showed that the strength of samples increased with increasing pore pressure and effective confining pressure. With increasing pore pressure and decreasing effective confining pressure, the stress-strain curves for the samples changed from strain-hardening to strain-softening. By analyzing the Mohr envelops, the cohesion was found to increase with increasing pore pressure. Moreover, the failure stress points lines for the samples were influenced by the pore pressure. A shift point was introduced, and it occurred at a certain pore pressure value between the strain hardening and strain softening behavior of the hydrate-bearing samples. Additionally, the value of the shift point was found to change with effective confining pressure.