Methane Hydrate-Bearing Sediments (HBS) are natural soil deposits which contain methane hydrate in their pores. Recent studies have shown that the existence of methane hydrate significantly influences their mechanical behavior. However, the underlying microscopic mechanism of the influence is still poorly understood due to the limitation of laboratory tests. This paper presents an investigation on the geomechanical behavior of HBS by using the Discrete Element Method (DEM). In the simulation, soil grains were simulated using graded aggregates of diameters ranging from 0.1 to 0.4 mm, and methane hydrate was simulated using particles of a diameter of 0.06 mm which bonded with the soil and other hydrate particles at the contacts. And then a series of numerical simulations of drained triaxial tests were performed on HBS samples with different hydrate saturations and under different confining pressures. The simulation results are qualitatively similar to the test data, which demonstrates that the modeling method proposed in this paper is reasonable. From the investigation, it can be concluded that, besides the reduced porosity, the increased bond number in HBS samples due to the increase of hydrate saturation also contributes to the enhancement of the peak strength, elastic modulus and dilation of HBS, and the contribution diminishes as the axial strain increases. Furthermore, the results show that the influence of the confining pressure on the mechanical properties of HBS stems from the densification but not the bond.
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