Static and kinematic damage characterization in structured sand: Fid-Bau Portal

Static and kinematic damage characterization in structured sand

Shen, Zhifu / Jiang, Mingjing / Wang, Shengnian

Abstract Damage is the key process controlling the behavior of cemented geomaterials, such as structured sand. Damage characterization of structured sand is studied based on granular material mechanics with the aid of discrete element method (DEM) simulation in this paper. Structured sand is viewed as a mixture of remolded and structured parts, whose behavior is defined by the collective responses of unbonded and bonded contacts, respectively. Based on the cross-scale links between macroscopic quantities (stress and strain) and microscopic quantities (contact force, contact position and relative motion of particles), stresses and strains of the two parts are assembled to arrive at the overall stress and strain of structured sand. The weights of the two parts in stress and strain assembling/partitioning emerge naturally as a stress-based static damage variable and a strain-based kinematic damage variable, respectively, which are then evaluated using the DEM simulation results. The static damage variable captures the role of remolded part in load-bearing structure of structured sand, while the kinematic damage variable describes the spatial geometric configuration of the two parts. Both damage variables increase with deviator strain in a sigmoidal pattern. Directional damage indexes indicate that damage is isotropic from the view of kinematic response, but it is anisotropic if examined from static point of view. The degree of anisotropy in static damage is influenced by external stress conditions and internal microstructure anisotropy. This study provides a physically robust and theoretically rigid framework for the development of a micromechanics-based constitutive model of structured sand.