Influence of Effective Confining Pressure and Consolidation Method on the Hydrate Formation Efficiency and Mechanical Properties of Hydrate-Bearing Clayey-Silty Sediments

Studying the mechanical properties of hydrate-bearing clayey-silty sediments (HBCSs) is vital for safe hydrate exploitation. Currently, various methods are employed in the laboratory for preparing HBCS samples, but there is a lack of evaluation on hydrate formation efficiency under different effective confining pressures. Therefore, to enhance the accuracy and comparability of the HBCS laboratory test, this study investigates the formation efficiency of hydrates under different effective confining pressures by analyzing methane gas consumption. Meanwhile, to simulate the growth environment of real submarine hydrates, the “simultaneous formation and consolidation (SFC)” method was adopted. The test results indicate that the effective confining pressure has a significant influence on the hydrate formation efficiency. Taking effective confining pressures of 0.2, 0.5, 1, 3, and 5 MPa as examples, the hydrate formation efficiency is relatively higher at 0.5 MPa. The consolidation method of HBCS has an important influence on its mechanical properties. Through triaxial shear tests, it is found that SFC enhances the strain-hardening tendency of HBCS; improves its failure strength, secant modulus, and internal friction angle; and reduces cohesion. The influence of confining pressure and hydrate saturation on the stress–strain curves and mechanical parameters of HBCS does not change with a change in the consolidation method.