DEM investigation on mechanical properties of methane hydrate bearing soils under different temperatures and pore-water pressures

Mechanical properties of methane hydrate bearing soils (MHBS) are influenced by the surrounding temperature (T) and pore-water pressure (σ_w). Study on such influence is of great significance for the safe exploration of methane hydrate. Firstly, a thermal-hydro-mechanical bond contact model is introduced to capture the microscopic contact behavior of methane hydrate bonded granules. Secondly, the model is implemented into the distinct element method (DEM) to simulate DEM biaxial tests of MHBS for different T and σ_w. Finally, the influence of T and σ_w on the macro-mechanical properties of MHBS is discussed by analyzing the results from the DEM biaxial tests and the laboratory tests. The results show that the DEM biaxial tests incorporating the bond contact model can efficiently capture the influence of T and σ_w on macro-mechanical properties of MHBS. T and σ_w affect the mechanical properties of inter-particle methane hydrate and in turn influence the macroscopic mechanical behavior of MHBS. A dimensionless parameter L, which is calculated in the coordinates of ordinate and abscissa being dimensionless σ_w and T respectively as the minimum distance from a point of dimensionless σ_w and T to the phase equilibrium line, is advised to use for evaluating the macro-mechanical properties of MHBS with respect to different T and σ_w.