DEM investigation of the mechanical behavior of frozen soil along various stress paths

Understanding the mechanical characteristics of frozen soil is critical for engineering projects in cold regions. A series of case studies were conducted to explore the macroscopic and microscopic mechanical behavior of frozen soil during four different stress paths, i.e., isotropic, constant stress ratio, conventional triaxial, and true triaxial compression tests, using the distinct element method (DEM). The particle-scale mechanism and temperature effect of frozen soil are also taken into account in the DEM simulation. The results indicate that the peak stress/yield stress of frozen soil decreases with the increase of temperature or decrease of stress ratio or decrease of intermediate principal stress ratio b, which is related to the evolutions of bond breakage, bond stress, mechanical coordination number, and deviatoric fabric. When 0.25 ≤ b ≤ 0.75, the direction of strain increment deviates from the direction of stress. In addition, the relationship between the damage variable B and the volumetric strain ε_v or shear stain ε_s can be expressed as \(B=1-\mathrm{exp}(-a\cdot {\varepsilon }_{v}^{n})\) or \(B=1-\mathrm{exp}(-a\cdot {\varepsilon }_{s}^{n})\) under different stress paths. The simulation results and revealed microscopic mechanism will be valuable in developing breakage-mechanics-based constitutive models for frozen soil.