Coupled Control of Fines Content and Morphology on the Critical State and Fabric Evolution of Binary Granular Mixtures

ABSTRACT This study investigates the coupled control of fines content ( f c ) and fine particle morphology ( P ) on the macro‐micro shear behavior of binary granular mixtures using coupled DEM‐FDM simulations. A series of drained triaxial compression tests were performed on mixtures with varying f c and different P . The results reveal a pronounced non‐monotonic dependence of shear behavior on f c . Both the peak friction angle and maximum dilation angle increase initially and reach their maxima at intermediate f c before decreasing as the coarse‑particle skeleton is progressively disrupted. In contrast, the critical state friction angle is primarily governed by P and exhibits a clear correlation with overall particle regularity O R . Divergent critical state lines observed in the conventional e ‐ p ′ space collapse into a single line when expressed using a modified equivalent skeleton void ratio that incorporates O R . Microscopic analysis shows that shear strength evolution is controlled by a structural transition in the contact network, from a coarse‑dominated skeleton at low f c to a fines‑dominated contact network at high f c . The anisotropy of normal contact forces is identified as the dominant contributor to macroscopic strength. These findings provide new insights into the coupled influence of fines content and fine particle morphology on the mechanical behavior of binary granular soils.