Technical PaperMacro and micro behaviour of methane hydrate-bearing sand subjected to plane strain compression

For methane hydrate production, it is essential to understand the mechanical behaviour related to safety and efficiency. Plane strain compression tests were carried out to investigate the macro and micro behaviour of both the MH-bearing sand and the host sand. It was found that whilst there were no clear peak stress ratios in the TC results, the PSC results showed a marked increase in the peak stress ratios, regardless of whether or not MH was included. The peak strength increased due to MH, and the dilative behaviour of the MH-bearing sand occurred more markedly than that of the host sand. As the confining pressure increased, the peak strength decreased and the volume change became contractive. Deformation in the shear band was suppressed as the confining pressure increased for the host sand, whereas contractive and dilative behaviour occurred in the shear band for the MH-bearing sand regardless of the level of confining pressure. The thickness of the shear band for the MH-bearing sand appeared to be thinner than that for the host sand and there was no dependence on the confining pressure. As the confining pressure increased, the occurrence of particle crushing also increased. Coefficient of uniformity Uc, inside the shear band, was 1.7 times larger than the original Uc of the host sand when σ3′=5MPa.