Particle breakage behavior of silty loess: Insights based on experimental tests, image analysis, and numerical simulation

Abstract

Particle breakage in loess during consolidation and shear has been documented; however, quantitative research on the mechanical and microstructural responses during breakage remains limited. This paper provides a detailed analysis of the breakage behavior of silty loess at the continuum scale using ring shear tests, image processing, and numerical simulations. The results show the following. (1) The dominant size range of broken particles is 0.03–0.08 mm, and the relative breakage (B_r) increases with the stress and shear displacement. Particle breakage significantly reduces the median particle size and peak shear strength of the soil, alters the residual strength parameters, and delays the onset of the residual state. The primary stress mode leading to breakage is shear, rather than impact stress, and the complex microstructure of the particles substantially affects their breakage potential. (2) Conical contact is dominant between loess particles, and the breakage mode can be simplified to a central crack. The critical particle size for the coordination number is 5 μm. Breakage causes a higher growth rate in the average coordination number of the particles, with contact directions converging toward the shear direction. The coefficient of variation (C_V) of the clay coating distribution is significantly correlated with the B_r, with a higher B_r indicating a more homogeneous distribution. (3) The particle elongation index (EI) tends to increase, the surface roughness is lower, and the circularity fluctuates between 0.66 and 0.72. The fracture mechanisms of the particles, rather than their initial morphology affect these parameters. This study provides enhanced insights into particle breakage and the mechanical responses from microstructural to macroscopic scales.