Discrete element analysis of geogrid–aggregate interface shear behavior under cyclic normal loading

The stability of a geogrid-stabilized structure affected by cyclic normal loading (CNL) is significant but has not been fully revealed. Using the discrete element method (DEM), the effect of CNL on the microscale mechanical responses (i.e., stress states, contact evolution, fabric deformation) of the geogrid–aggregate interface direct shear test is first investigated. The complex shear behaviors at the interface with normal cyclic excitation at different frequencies and amplitudes are simulated. The DEM model is able to capture the macroscopic dynamic shear laws at the geogrid–aggregate interface in a similar way to those tested experimentally. The detailed behavior of the aggregate interacting with the geogrid under CNL is investigated. Compared with the simulation under static normal loading (SNL), CNL makes the stabilized layer more prone to failure, which could be quantitively evaluated by analyzing the local shear strain and the interparticle interlocking level. Microscale studies on the load wave propagation process and the confinement zone indicate that the present method can provide an applicable tool for dynamic service assessment and reliable forecasting of the undesirable effect of CNL on a mechanically stabilized layer.