A microfocus x-ray computed tomography based gas hydrate triaxial testing apparatus.

Abstract

Gas hydrate-bearing sediment shows complex mechanical characteristics. Its macroscopic deformation process involves many microstructural changes such as phase transformation, grain transport, and cementation failure. However, the conventional gas hydrate triaxial testing apparatus is not possible to obtain the microstructure in the samples. In this study, a novel, low-temperature (-35 to 20 °C), high-pressure (>16 MPa confining pressure and >95.4 MPa vertical stress) triaxial testing apparatus suitable for X-ray computed tomography scanning is developed. The new apparatus permits time-lapse imaging to capture the role of hydrate saturation, effective stress, strain rate, hydrate decomposition on hydrate-bearing sediment characteristic, and cementation failure behavior. The apparatus capabilities are demonstrated using in situ generation of hydrate on a xenon hydrate-bearing glass bead sample. In the mentioned case, a consolidated drained shear test was conducted, and the imaging reveals hydrate occurrence with a saturation of 37.3% as well as the evolution of localized strain (or shear band) and cementation failure along with axial strain.