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Particle shape modulates the contrasting scale effects in the mechanical behavior of rockfill materials and sandy gravel
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DOI：10.1016/j.compgeo.2026.108504.png)
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Abstract
En 中文
Scale effect is a major source of inaccurate deformation prediction in rockfill dams. Previous studies have shown that rockfill and gravel materials exhibit contrasting scale-dependent responses, but the underlying mechanism remains poorly understood. In particular, how particle shape contributes to these contrasting scale effects has not been systematically clarified. This study investigates the coupled effects of particle shape and breakage strength on the scale effect of granular materials using a discrete element method framework. Rockfill, sandy-gravel and spherical assemblies with different maximum particle sizes were compared under unbreakable and breakable conditions, and their macroscopic and microscopic responses were analyzed. The results show that particle shape plays a key role in controlling the differences in scale effect. Under unbreakable conditions, the initial tangent modulus Ei and tangent bulk modulus Bt of rockfill decrease with increasing particle size, whereas sandy-gravel and spherical assemblies show a scale-strengthening trend. This contrast is governed by the combined effects of packing heterogeneity, effective contact support and force-chain directionality. The coefficient of variation CVϕ and interquartile range IQRϕ of the local packing fraction increase markedly for large rockfill specimens, indicating increasingly heterogeneous packing. The mechanical coordination number of rockfill also decreases with particle size, suggesting fewer effective contacts per particle. Larger particles carry stronger normal forces, but their principal-stress-direction projection and force anisotropy both decrease in rockfill, while the opposite occurs in sandy gravel and spheres. Particle breakage further modifies this shape-dependent scale effect: reducing breakage strength intensifies the scale weakening of rockfill but weakens the scale effect of sandy-gravel and spherical assemblies.
Keywords:
Rockfill
Scale effect
Particle shape
Discrete element method
Particle breakage
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