Discrete element modeling of the effect of particle size distribution on direct shear behavior of hydrate-bearing sediments

Abstract

Natural gas hydrates are a new energy resource with a great potential for commercial exploitation. The exploitation of natural gas hydrate can cause a degradation of the mechanical properties of hydrate-bearing sediments (HBS) and may trigger geohazards. Natural gas hydrates exist widely in marine sediments which have different types of sediment matrix with different particle size distributions (PSD). The effect of the PSD of hydrate-bearing sediments has not been investigated clearly. In this paper, a direct shear test model of HBS is built using the discrete element method. A series of numerical simulations with different PSD of HBS under different hydrate saturations and vertical stresses are conducted. The results show that the shear strength, residual strength, and dilatation of HBS increase with increasing hydrate saturation at the same PSD. It is found that the mechanical properties of HBS are not sensitive to the PSD at the same median particle size at low vertical stress. However, the shear strength can be enhanced with the increase of median particle size. The results obtained in this study can facilitate a deep understanding of the mechanical properties of HBS.