Abstract: A new multi-functional triaxial testing system for hydrate-bearing sediments was developed. The system was consisted of a gas charge/discharge module, a stress loading module, a temperature control module, a data acquisition module, and an auxiliary module. High-pressure liquid pumps were used to generate confining pressure and axial pressure under the modes of constant pressure, constant flux, gradient pressurization, and gas pressure tracking. Therefore, the syntheses of differently conditioned hydrate-bearing sediments and triaxial shearing of samples could be achieved. The function of confining pressure tracking gas pressure kept the net confining pressure unchanged during the hydrate formation process, which ensures the consistency of initial conditions of the samples. The volumetric deformations of the samples could be measured by the volume change of the confining liquid, and the gas pressure could be controlled by adjusting the back pressure regulator. Hence, the decomposition process of hydrate-bearing sediments under different pressure reduction rates could be modelled. Triaxial specimens were made of clayey fine sand and carbon dioxide. The hydrate syntheses, triaxial shearing tests, and decomposition tests were carried out to verify the reliability of the testing system.

Key words: hydrate, triaxial test, research and development, volumetric strain, decomposition