Three-dimensional DEM investigation of the stress-dilatancy relation of grain-cementing type methane hydrate-bearing sediment

Abstract

In this study, the Discrete Element Method (DEM) was employed to investigate numerically the effects of hydrate cementation and intermediate principal stress on the stress-dilatancy relation of grain-cementing type methane hydrate-bearing sediment (MHBS) by conducting a series of conventional and true triaxial tests. A novel 3D thermo-hydro-mechanical-chemical (THMC) contact model for MHBS was employed. The numerical results show that with increasing hydrate saturation and back pressure, or decreasing confining pressure, temperature and salinity, the stress-dilation relation of grain-cementing type MHBS evolves from dilation-dominant to bond-dominant. For the clean sand samples, the relationship between the normalized stress ratio η/Mcr and the dilatancy rate d is close under different intermediate principal stress coefficients. However, for the MHBS samples, this relationship is still affected by the intermediate principal stress coefficient b, due to the effect of hydrate cementation.

Keywords

• Stress-dilatancy
• Cementation
• Methane hydrate bearing sediment
• Discrete element method
• Intermediate principal stress