Three-dimensional discrete element modeling of the shear behavior of cemented hydrate-bearing sands

Abstract

Understanding the shear behavior of hydrate-bearing sands is fundamental for the safe exploitation of natural gas hydrates. Calibration is necessary to accurately capture the shear behavior of hydrate-bearing sands when using the three-dimensional discrete element method (DEM). In this study, a new method is developed to quantify the hydrate saturation of hydrate-bearing sands by using a DEM model with Voronoi partitions. A series of DEM simulations with various hydrate saturations and confining pressures were performed to calibrate the DEM model, which was then compared with experimental results. The results demonstrate that the DEM can effectively capture the macroscopic properties, including the shear strength, secant modulus, cohesion, and friction angle of hydrate-bearing sands. The bond strength and inter-particle friction coefficient of hydrates mainly impact the shear strength of hydrate-bearing sands, whereas the bond stiffness of hydrates affects both the shear strength and secant modulus of hydrate-bearing sands. The number of broken hydrate-sand bonds is much larger than the number of hydrate-hydrate bonds, indicating that the contribution of the former bonds is more significant than the latter bonds during the shearing process. This calibration method helps improve the reliability and accuracy of the DEM simulations for hydrate-bearing sands under triaxial compression tests.