Effects of particle size‐shape correlations on steady shear strength of granular materials: The case of particle elongation

Abstract

Granular materials often present correlations between particle size and shape due to their geological formation and mechanisms of weathering and fragmentation. It is known that particle shape strongly affects shear strength. However, the effects of shape can be modified by the role the particle plays in a sample given its size. We explore the steady shear strength of samples composed of particles presenting size‐shape correlations and we focus on the case of particle elongation in two opposite scenarios: (A) large elongated grains with finer circular grains and (B) large circular grains with elongated finer grains. By means of numerical simulations, we probe the shear strength of samples of varying particle size span from mono to highly polydisperse and particle aspect ratios varying between 1 and 5. We find that the two correlations tested strongly impact the shear strength as particle size span evolves. Microstructural analyzes allow us to identify how each correlation affects connectivity and anisotropies linked to the orientation of the particles and load transmission. Decompositions of the stress tensor let us identify the sources of the different mechanical behavior in each correlation and determine the contributions of each particle shape to macroscopic shear strength. This study proves that common small‐scaling methods based on truncated or parallel particle size distributions can incur in under/over‐estimations of shear strength if particle shapes are not considered in the scaling process.

Shear strength of angular granular materials with size and shape polydispersity

“…Together with a previous research on the effects of particle size-elongation correlations [Carrasco et al, 2022], this work proves that different grain size-shape correlations can have major effects on the critical shear strength and solid fraction of granular assemblies. These facts suggest that scaling methods based on scalping or parallel psd can imply significant errors when estimating the shear strength of a material in a small-scaled sample if grain shapes are not taken into account in the procedure.…”

“…The main objective of this paper is to study the effects of grain size-shape correlations and psd on the critical strength of granular materials. This research extends the work of Carrasco et al [2022], which presented the effect of particle elongation correlated with grain sizes by introducing a comprehensive analysis of the effects of grain angularity and grain geometric irregularity. We use discrete element modeling (DEM) of 2D granular samples over a large range of psd and analyze the results regarding the macromechanical behavior under critical state conditions.…”

Particle size distribution (PSD) estimation using unmanned aerial vehicle (UAV) photogrammetry for rockfill shear strength characterization

“…This approach presumes that the adjusted PSD is comparable to the original grading in stress-strain behavior. However, changes in particle size may alter individual grain properties, including shape and crushing strength [25]. Although parallel scaling is a common technique in rockfill materials [39], the effects of particle size correlations are not often considered, and their impacts are not thoroughly understood [29].…”

Generation of 3D geotechnical particles using random angular bend algorithm

“…When the simulation of geo‐materials is performed utilizing discrete element method (DEM), their mechanical behaviors are closely related with the micro‐structures of generated rock/soil mass 2,3 . To accurately reflect the mechanical behaviors of geo‐materials, the simulation of micro‐structure of rock‐soil mass plays an important role in the subsequent modeling, in which the selection of generating method (including overlapping check method and throwing method of particles) of particle shape is more significant for reflecting the micro‐structure 4,5 . Reproducing the micro‐structure of geo‐materials and establishing the relationship between micro‐structure and macro‐behaviors are efficient measures to explore the mechanical behaviors of geo‐materials and are also pivotal for revealing failure mechanism and patterns in multi‐scales and improving design and construction quality 6,7 …”

“…2,3 To accurately reflect the mechanical behaviors of geo-materials, the simulation of micro-structure of rock-soil mass plays an important role in the subsequent modeling, in which the selection of generating method (including overlapping check method and throwing method of particles) of Method proposed in the paper Concave / convex polyhedron Yes particle shape is more significant for reflecting the micro-structure. 4,5 Reproducing the micro-structure of geo-materials and establishing the relationship between micro-structure and macro-behaviors are efficient measures to explore the mechanical behaviors of geo-materials and are also pivotal for revealing failure mechanism and patterns in multi-scales and improving design and construction quality. 6,7 To accurately generate the particles with arbitrary shape, plenty of researches have been conducted about the generation of 2D or 3D random particles.…”