Bonded particle model for dilated polyhedron considering fracture modes and its application to lateral resistance of ballast bed in cold regions

Considering the spatial arrangement characteristics of bonded irregular particle systems, this paper first constructs irregular dilated polyhedron elements based on the Voronoi cutting algorithm and Minkowski Sum theory. Subsequently, by extending the traditional sphere-based BPM (Bonded Particle Model) to irregular particle elements, a novel dilated polyhedron bonding-breaking model considering different fracture modes is developed under arbitrary contact modes. A collision example between two bonded square particles and a rigid plate is adopted to verify the stability of the model. Later, the difference between the tensile-shear fracture mode and the mixed fracture mode with damage process for contact bond is compared by the discrete element simulations of the tension-fracture behavior between two bonded square particles and the uniaxial compression simulation of frozen ballast aggregate. Finally, the influence of section size on the lateral resistance of the ballast bed structure at low temperatures is discussed using the dilated polyhedron BPM. The results showed that the developed dilated polyhedron BPM considering different fracture modes can realize mechanical behaviours between bonded irregular particles. Compared with the tensile-shear fracture mode, the mixed fracture mode not only considers the combined effect of normal and tangential stress on the bond but also realizes the damage deformation and stiffness attenuation of the bond, which can achieve the “delayed” fracture effect. Meanwhile, the model also shows good reliability in analyzing large-scale engineering problems, such as the mechanical performance of low-temperature ballast beds. The research effectively develops the bonding and breaking model of irregular elements and provides a new perspective for the contact-bond-fracture behavior simulation of irregular granular materials.