DEM Analysis of Geomechanical Properties of Cemented Methane Hydrate-Bearing Soils at Different Temperatures and Pressures

Mechanical properties of methane hydrate-bearing soils are influenced by the surrounding temperature and pore pressure. Studies of such influences are of great significance for the safe exploration of methane hydrate. First, a thermo-hydro-mechanical bond contact model is introduced to elucidate the microscopic contact scale behavior of grains with methane hydrate bonds. Second, such a model is incorporated into the distinct-element method (DEM), and a dimensionless temperature-pressure distance parameter is introduced. The influences of temperature and pore pressure along heating and depressurization paths are analyzed by conducting DEM biaxial compression tests, which are also compared with the results of laboratory triaxial compression tests conducted by others. The variation rules of the macromechanical properties (i.e., strength, elastic modulus, peak friction angle, cohesion, and dilatancy angle) with changing temperatures and pore pressures are then analyzed for different effective confining pressures and methane hydrate saturations in the DEM biaxial compression tests, which helps to provide an initial reference for practical applications. Finally, the microscopic mechanisms that affect the macromechanical characteristics are investigated via the ratio of intact bonds under different loading conditions. The results demonstrate that the DEM biaxial compression tests incorporating the bond contact model can efficiently capture the influences of temperature and pore pressure on the macromechanical properties of methane hydrate-bearing soils. It is shown here that temperature and pore pressure affect the mechanical properties of interparticle methane hydrate and, in turn, influence the macroscopic mechanical behavior of methane hydrate-bearing soils. (C) 2015 American Society of Civil Engineers.