Investigation of particle-scale mechanical behavior of hydrate-bearing sands using DEM: Focus on hydrate habits

Natural gas hydrates are commonly found in onshore permafrost and seabed regions. Hydrates often exhibit different pore habits in different regions, which may affect the mechanical behavior of hydrate-bearing sands (HBSs). In this study, pore-filling, load-bearing and cementing HBSs were prepared using discrete element method (DEM). The numerical biaxial compression tests show that the digital cementing HBS specimen well capture the stress-strain response of the gas-saturated HBS specimen in experiments under sigma c = 3 MPa, which justify the DEM model in this study. The pore-filling hydrates contribute little to the stress-strain response of sediments, while the load-bearing and cementing hydrates significantly enhance the failure strength and stiffness, and also induce strain-softening behavior and higher volume dilation. Hydrate cementation hinders the lateral fabric development in HBS, and renders orderly particle displacement and abundant strong force chains. The yielding of HBS is dominated by the buckling of strong force chains. Particle sliding, dislocation and rotation are responsible for the formation and development of shear bands, which governs the volume dilation and nonuniform deformation of HBS. Comprehending the geomechanical behavior of HBS under different hydrate habits facilitates the optimization of engineering solutions for hydrate exploitation.