SPH-based numerical simulation of uniaxial compression of concrete with random polygonal aggregates

Random polygonal aggregates represent the most realistic morphology of aggregates in the mesostructure of concrete. Their angular characteristics and spatial distribution play a decisive role in the stress concentration, crack initiation, and planar structural response of concrete under uniaxial compression. Consequently, in-depth investigation into this subject is essential for revealing the fundamental mechanisms underlying the macroscopic mechanical behavior of concrete. To this end, this paper proposes a simulation method for uniaxial compressive failure of concrete based on smoothed particle hydrodynamics and develops a proprietary particle generation program for random polygonal aggregates. The proposed method adopts a Mohr–Coulomb criterion with tensile cutoff as the failure criterion and introduces a modified smoothing kernel function to accurately simulate spontaneous crack initiation and propagation. In terms of aggregate modeling, the separation axis theorem and ray casting method are employed to achieve automatic generation of random polygonal aggregates satisfying geometric constraints and precise classification of particle properties. Through three sets of comparative numerical examples, the effects of aggregate quantity (30, 40, 50), particle size range (4–8 mm, 4–10 mm, 4–12 mm), and effective weak interfacial zone (EWIZ) width (0.5 mm, 1.0 mm, 1.5 mm) on the two-dimensional plane-strain failure patterns of concrete are systematically investigated. The results indicate that an increase in aggregate density or a widening of the particle size range enhances the material’s brittleness within this 2D simulation framework, promoting a transition in the 2D-simulated planar failure pattern from “localized shear” to “diffuse cracking”. In contrast, an increase in the thickness of the interfacial transition zone induces a similar transition in 2D-simulated plane-strain planar failure patterns from “localized shear” to “diffuse cracking”, and reduces peak stress while increasing peak strain, which substantially enhances the material’s ductility in the 2D numerical system. Comparative verification with existing results demonstrates good agreement in terms of 2D-simulated failure morphology and crack evolution. It is worth noting that the simulated 2D failure patterns cannot be directly equated to the real 3D failure morphology of concrete, but this classification effectively reflects the meso-damage concentration and dispersion law under unified numerical conditions, supporting comparative parametric analysis. This study provides an efficient modeling approach and theoretical support for two-dimensional mesomechanical qualitative analysis of concrete with irregular aggregates, and its quantitative conclusions cannot be directly extrapolated to three-dimensional structural members without further correction.