Observations on fabric evolution to a common micromechanical state at the soil‐structure interface

Abstract

Summary 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.

3D DEM simulations of monotonic interface behaviour between cohesionless sand and rigid wall of different roughness

“…In [55], the boundary conditions along the horizontal rigid wall suggested inclusion of two ratios connected to the normalized wall roughness (a ratio of the micro-polar rotation multiplied by the mean grain diameter and the horizontal displacement and a ratio of the horizontal shear stress multiplied by the mean grain diameter and the horizontal couple stress). To better understand microscopic phenomena during wall friction, DEM calculations were also carried out [4,5,12,14,15,22,24,25,62,63,70,77,78]. There exist many numerical studies of wall friction using DEM under 2D conditions (e.g.…”

“…There exist many numerical studies of wall friction using DEM under 2D conditions (e.g. [14,15,22,62,63,77,78]) and only a few under 3D conditions [4,5,12,24,25,70]. To facilitate the interpretation of macroscale responses, microscale metrics such as contact normal force distribution, contact networks, mobilization of friction, and particle rotation were calculated to elucidate the wall friction mechanism.…”

Novel approach to apply existing constitutive soil models to the modelling of interfaces

“…In addition, these characteristics have also been reproduced using the discrete element method. [54][55][56] (A) (B)…”

Closure to “Effect of Grain Size Distribution of Sandy Soil on Shearing Behaviors at Soil–Structure Interface” by Han-Lin Wang, Wan-Huan Zhou, Zhen-Yu Yin, and Xi-Xi Jie

“…1 are the interface friction angle at both the dry and the saturated states. the effect of water content, the shearing behavior of the soilstructure interface is also influenced by the grain size distribution (Liang et al 2017;Han et al 2018; the original paper), the structure roughness (Potyondy 1961;Han et al 2018;Jing et al 2018;Tovar-Valencia et al 2018;Zhu et al 2018), the soil type including the particle sphericity and the initial fabric (Zhou et al 2019;Zhu et al 2019), the plasticity (Potyondy 1961), and the loading condition (Potyondy 1961;Chen et al 2020b), among others. To establish a larger database for the shearing behavior at the soil-structure interface, more studies are definitely needed.…”