Development of DEM Model of Methane-Hydrate Bearing Sand Layer

Abstract

The goal of this study is to simulate the mechanical strength of the methane-hydrate bearing sand layers in a microscale computational domain filled with sand particles, hydrate, and water using the discrete element method. For this purpose, we have developed a cement-type coupling model in which methane hydrate intervenes between sand particles. A computational domain was prepared for the tri-axial compression test of a cylindrical specimen, and the specimen domain was filled with glass beads so as to match the particle size distribution used in the experiment in the literature with a porosity of 0.4. The specimen was compressed by moving the wall surface installed above and below the specimen. The stress was calculated for various methane hydrate saturation. At all restraint pressures, the axial stress increases with almost the same slope after the start of compression. The larger the restraining pressure, the larger the peak of the axial stress. The axial stress, which was initially 1 MPa, peaked and then decreased sharply, exhibiting marked strain softening. The calculated results are in good agreement with the experiments, and it was found that this model can simulate the experiment well at different confining pressures and methane hydrate saturation.