A vector based DEM approach for modelling geogrid in railway ballast layer

The geogrid stabilization in railway ballast is achieved through the effective interlocking and confinement on ballast particles. This study proposes a vector cementation model (VCM) integrated into the discrete element method (DEM) to analyze the micro-to-macro behavior of ballast-geogrid interlocking, offering fundamental insights into their structural and mechanical properties of geogrid interlocking with ballast particles. Based on this model, the bonding deformation in geogrid is simulated, demonstrating the effectiveness and applicability of the proposed method. The proposed model is first verified with the cantilever beam shear deformation and uniaxial compression tests on concrete. Upon verification of its accuracy, the tensile-compressive and bending deformations of geogrids connected by Timoshenko beams, as well as their influence on the movement of ballast particles, were analyzed in the discrete element method (DEM). It was found that: The vector cementation model can accurately predict the bending and shearing deformation of cantilever beam, with all relative errors below 1%; The proposed model demonstrates the capability to accurately simulate macroscopic mechanical responses, including differential settlement behavior in geogrid-reinforced systems. Furthermore, it elucidates the fundamental stabilization mechanisms of geogrids, thereby offering a new approach for continuum-discrete hybrid modeling framework for geotechnical applications.