Discrete element modelling of methane hydrate soil sediments using elongated soil particles

Abstract

In this Discrete Element Modelling research, triaxial compression tests of particle assemblies were simulated to study the mechanical behaviour of methane hydrate sediments with two different hydrate formation patterns: pore-filling and cementation. The soil particles were modelled using spherical or elongated particles (two aspect ratios 1.5 and 2.0). Hydrates were modelled as smaller particles and were placed either inside the pores in a random manner (the pore-filling case) or around the soil particle contacts (the cementation case). Compared to the pure soil samples, the hydrates essentially influenced the mechanical behaviour of the hydrate-bearing soil samples, and the behaviours varied due to the different hydrate growth patterns. The behaviour with elongated soil particles is much closer to that of the natural hydrate-bearing sandy sediments retrieved from the Nankai Trough than the behaviour with spherical particles. The observed macroscopic strength behaviour is also explained by the microscopic contact-type related contributions (soil-soil contact, soil-hydrate contact and hydrate-hydrate contact) to the deviatoric stresses.

Micromechanical Investigation of Stress Relaxation in Gas Hydrate-Bearing Sediments Due to Sand Production

“…For examining the MH influence on stress relaxation, the DEM numerical analyses need to be extended for representing MH sediments. DEM models for MH can roughly be divided into three categories: (1) models where the hydrate is represented as particles seeded in the pores within the sand and hydrate is not part of the soil skeleton and, consequentially, there is no effect on the stiffness and a small effect on the strength were obtained (e.g., [61]); (2) models in which the hydrate is represented by bonding sand particles and the bond properties (e.g., strength, stiffness) are a function of the hydrate saturation, without a real volume of hydrate (e.g., [32,62]); (3) models in which the hydrate particles are bonded to sand particles, with a considerable effect on initial stiffness and volumetric dilatancy (e.g., [30,63]). Recent studies indicate that the contribution of the hydrate to the strength of the soil is mostly of a frictional nature, rather than cohesive [26,60,64].…”

Influence of Fines Content on the Mechanical Behavior of Methane Hydrate‐Bearing Sediments

“…The simulated strengths of the pore‐filling and cementing types of hydrate‐bearing sediments classified by Dai et al () and Waite et al () were obtained using different values of fitting parameters to interpret the influence of hydrate morphology on the mechanical properties. Brugada et al (); Jung et al (); Shen and Jiang (); Xu et al (); and Yu et al () conducted discrete element modeling to study methane hydrate‐bearing sediments using a microscopic contact and bonding method. The majority of the above experimental and numerical investigations were conducted on hydrate‐bearing sediments formed with coarse‐grained sands without fines content (FC).…”

A constitutive mechanical model for gas hydrate bearing sediments incorporating inelastic mechanisms

“…Geomechanics is a key component in the numerical modeling of engineering problems involving HBS. Several types of mechanical constitutive models for hydrate bearing sediment have been proposed in the last few years [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Only a few of them are discussed below.…”