A three-dimensional DEM modelling of triaxial test on gas hydrate-bearing sediments considering flexible boundary condition

Abstract

The discrete element method (DEM) has been widely used to investigate the mechanical properties of gas hydrate-bearing sediments (GHBS). However, a flexible membrane boundary has not been incorporated into three-dimensional DEM modelling. Moreover, the roles of hydrates in stress transmission have not been comprehensively interpreted from a particulate scale point of view. This study adopted the finite difference method (FDM)-discrete element method (DEM) coupling method to establish the flexible boundary condition to capture the failure modes of GHBS and categorized the overall contact set into three contact subsets (i.e., soil-soil, soil-hydrate and hydrate-hydrate contact subsets) in a way that the stress transmission characteristics of hydrates can be identified. The simulated macroscale mechanical responses demonstrate a favourable agreement against the experimental results. The results show that the sample with a low hydrate saturation shows a single slant shear failure zone, while the sample with a high hydrate saturation shows an X-shape shear failure zone. The particulate scale analysis shows that the soil-hydrate contact subset not only plays a critical role in stabilizing the strong force chains but also has a significant contribution to the deviatoric stress. By contrast, the hydrate-hydrate contact subset accounts for a small contribution to the deviatoric stress.

Keywords:

• gas hydrate-bearing sediments
• discrete element method
• triaxial test
• FDM-DEM coupled method
• flexible boundary
• contact subsets

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Science and Technology Major Project of China under Grant No. 2017ZX05009003-002; the National Key Research and Development Program of China under Grant No. 2017YFC0307604; Graduate Innovation Program of China University of Petroleum (East China) under Grant No. YCX2020071.