Effect of Particle Shape on Stress-Dilatancy Responses of Medium-Dense Sands

Abstract

The effect of particle shape on the strength, dilatancy, and stress-dilatancy relationship was systematically investigated through a series of drained triaxial compression tests on sands mixed with angular and rounded glass beads of different proportions (0%, 25%, 50%, 75%, and 100%). A distinct overall regularity parameter was used to define the particle shape of these mixtures, which ranged from 0.844 to 0.971. The test results showed that all of the samples at an initial relative density of 0.6 exhibited strain-softening and volume-expansion behavior. It was found that the peak-state deviatoric stress, peak-state axial strain, and peak-state friction angle at a given confining pressure decreased with increasing overall regularity. The maximum differences in the peak-state deviator stress, peak-state axial strain, peak-state friction angle, excess friction angle, and maximum dilation angle due to changes in particle shape could be as much as 0.61 MPa, 5.4%, 8.6, 1.5, and 3°at a given confining pressure of 0.4 MPa. In addition, it was found that the slope of the relationship between the peak-state friction angle and maximum dilation angle was independent of the particle shape, whereas the intercept (i.e., the critical-state friction angle) was significantly influenced by the particle shape. A stress-dilatancy equation incorporating the effect of overall regularity was proposed and provided a good estimate of the observed response accounting for the different particle shapes investigated.

Thermal Conductivity of Granular Soil Mixtures with Contrasting Particle Shapes

“…Particle shape can be characterized by three parameters, the aspect ratio ( R A ), convexity ( X C ), and sphericity ( C S ) (Yang and Luo 2015;Xiao et al 2019). These parameters were determined from binary images of two kinds of glass particles using ImageJ (Schneider et al 2012), as shown in Figs.…”

“…It should be noted that the aspect ratio, convexity, sphericity and overall regularity can only reflect the particle shape of a single particle but not an assembly of particles. Following the studies of (Yang and Luo 2015;Xiao et al 2019), 500 rounded particles were randomly selected for testing their particle shape parameters and the cumulative distribution curve for each particle shape parameter was obtained for the rounded particle assembly. The particle-shape cumulative distribution curve for the angular particle assembly was obtained in the same way.…”

“…Particle shape has well-known effects on the characteristics of granular soils including packing density (Cho et al 2006;Shin and Santamarina 2013;Zheng and Hryciw 2016) and fabric (Maeda et al 2010;Turner et al 2016;Zhao and Zhou 2017), and also can have significant effects on mechanical properties like compressibility (Rousé et al 2008;Shin and Santamarina 2013;Gong and Liu 2017), shear modulus (Cho et al 2006;Shin and Santamarina 2013), shear strength (Varadarajan et al 2003;Guo and Su 2007;Rousé et al 2008;Yang and Wei 2012;Shin and Santamarina 2013;Yang and Luo 2015;Xiao et al 2019), dilation (Guo and Su 2007;Yang and Luo 2015;Xiao et al 2019), susceptibility to liquefaction (Tsomokos and Georgiannou 2010;Yang and Wei 2012; and Luo 2015), particle breakage during shearing (Afshar et al 2017;Cavarretta et al 2017), and failure mode during shearing (Alshibli et al 2017). Particle shape may also affect the hydraulic conductivity of granular soils (Côté et al 2011).…”

An Investigation on triaxial compression of flexible fiber packings

“…The effect of particle size distribution on yield stress is complex and depends on the shape of the distribution curve since the interaction between different particle species affects the overall stress. Particles of more angular shape (polyhedral particles, for example) have an increased chance of interlocking, causing a more anisotropic contact force network and a larger yield stress . More significant stress fluctuations are observed for flatter particles compared to rounder and more prolate particles due to the occurrence of avalanche‐like slip events .…”

A poly‐superellipsoid‐based approach on particle morphology for DEM modeling of granular media

“…In geomechanics applications, DEM users commonly employ idealized spherical discrete elements to simulate granular grains due to the advantages this may offer, including easy contact detection and high computational efficiency . However, numerical studies have proven that grain shape underpins various facets of the mechanical responses for granular materials and should be properly accounted for in their modeling . Irregular shape of grains, for example, has been found attributable to the increase in particle rotation/rolling resistance, the enhancement of particle interlocking, and hereby the overall strength of a granular material, when compared with simulations with spherical particles .…”