DEM simulations of the creep behavior of cemented methane hydrate-bearing sand

Abstract

The existence of methane hydrate can greatly influence the creep behavior of sediments, which remains largely unknown. The discrete element method is used to study the creep behavior of cemented methane hydrate-bearing sand. Methane hydrate is simulated as contact bonds between particles, and the bonding ratio is introduced to directly reflect the influence of hydrate saturation. The parallel-bar creep model is proposed to describe the damage development with time in the hydrate crystal, based on which a time-dependent bond strength equation is established to describe the creep behavior of hydrate as interparticle cementation. Reasonable consistency is found between the simulated and experimental results.The results show that methane hydrate bearing sand exhibits significant creep, which is similar to that of frozen sand. The microbehavior during creep is investigated, including the evolution of the local porosity, bond breakage, particle rotation, strong force chain, and deviator fabric, which show strong heterogeneity due to the gradual formation of shear bands. The underlying mechanism is explored, which is related to changes in the microstructure caused by bond breakage with time.