Observations on fabric evolution to a common micromechanical state at the soil‐structure interface
The fabric plays an important role in the mechanical behavior of granular material. The aim of this paper is to investigate the evolution of fabric in a soil‐structure interface (SSI) to a large shearing in an effort to clarify whether and how this form of fabric evolution can lead to a common microstructure. Using the discrete element method (DEM), two‐dimensional (2D) numerical interface shear tests were carried out, and certain macromechanical and micromechanical properties were exploited. All samples exhibited prominently localized strain in a zone covering the structure’s surface (named the localized zone), and much lower density and higher soil fabric anisotropy levels were found inside this zone than outside it. Disregarding different initial void ratios, a common critical state microstructure was observed in large shear deformations of soil samples, with essentially the same fabric arrangement in terms of contact orientation and internal force transmission. Due to the systematic forming, buckling, and collapsing of force chains, an angular zone (called an α‐zone), in which contact density was sluggish to varying degrees, appeared and extended around the main direction of the distribution of contact orientation inside the localized zone. The gradual deterioration of the force chains’ stability, as a result of an increasing void ratio, seemed to drive the α‐zone’s extension and lead to the rare variation of microstructures in the critical state.
Keywords: critical state, granular material, microstructure, soil fabric, soil‐structure interface, strain localization,