DEM-Based Study on the Mechanical Behaviors of Pore-Filling MHBS under Drained True Triaxial Conditions Varying the Intermediate Stress Ratio of Constant Mean Effective Stresses

Abstract

Methane hydrate-bearing soils (MHBS) are natural soil deposits that contain methane hydrate (MH) in the pores and have attracted a huge amount of attention as alternative energy to study mechanical properties for realizing large-scale commercial extraction. Especially, MHBS respond to applied loads under complex stress conditions, that is, the effect of the intermediate stress ratio on mechanical characteristics of MHBS. The effect of different values of intermediate stress ratios on the geomechanical responses of pore-filling MHBS was analyzed using the distinct element method (DEM). MH clusters are cemented together as agglomerates of spheres, which fill into the voids of the soil specimen according to the MH saturation. Then, the numerical pore-filling MHBS experimented with different loading paths of the true triaxial tests. Finally, the effects of the intermediate stress ratio on the mechanical characteristics of pore-filling MHBS were analyzed from two aspects, that is, macromechanical responses and micromechanical responses. The results showed that there were correlation analyses between the variations in the strong fabric and principal stresses. The friction angle increased with the intermediate stress ratio until it reached a peak value, and decreased thereafter. The Lade–Duncan criterion is approximately suitable to describe the three-dimensional strength of MHBS.