Micromechanical Analysis of Stress and Strength for Wet Granular Materials in Pendular State Based on Thermodynamics and DEM Simulations

ABSTRACT The stress and strength criterion in wet granular materials are derived on the basis of thermodynamics and discussed from micromechanics. The total stress expression is obtained from the energy relation between the discrete particle system and its equivalent continuum system, and then the effective stress tensor is obtained considering the thermodynamic conjugates to the strain tensor. The strength criterion at macroscale is rigorously deduced from the Coulomb‐type strength criterion at inter‐particle contacts based on thermodynamics‐based frameworks at macroscale and microscale. Furthermore, numerical simulations providing full access to micromechanical information are conducted using the discrete element method (DEM), which are used to discuss the stress and strength criterion in the pendular state: the total stress expression is validated with the aid of DEM; the capillary stress is controlled by both of water‐solid interfaces and air‐water‐solid contact lines on the matric suction 20 kPa, while on the matric suction 100 or 700 kPa the capillary stress is mainly controlled by water‐solid interfaces; the effective stress has enough micromechanical information to lead to a unique response that intrinsically belongs to the dry state; the frictional coefficient of strength criterion obtained from DEM is larger than the inter‐particle frictional coefficient and smaller than the upper limit value which supports the validity of the upper limit value derived from thermodynamics‐based approach.