This paper presents a discrete element method (DEM) investigation into the load transfer mechanisms and failure surfaces of geosynthetics reinforced soil (GRS) bridge abutments. A local strain-dependent reinforcement contact model is developed to accurately simulate the nonlinear tensile behavior of reinforcement. The study analyzes both the macroscopic deformation response and the microscopic fabric evolution of backfill soil under bridge load. The findings reveal that as the bridge load increases, the micro-bearing structure of the soil within the potential failure surface evolves through progressive loss of effective contacts, particle rotation, and fabric reorganization. These micromechanical phenomena underlie the development of shear bands and the global failure mechanism of GRS abutments. Furthermore, a parametric analysis is conducted to evaluate the effects of reinforcement stiffness, reinforcement vertical spacing, and backfill soil friction angle on failure surfaces of GRS abutments. The results demonstrate that higher reinforcement stiffness constrains failure surface development, while wider reinforcement spacing and lower soil friction angles lead to deeper and more pronounced failure surfaces. Overall, the study highlights the critical role of reinforcement-soil interactions and micromechanical processes in determining the deformation and failure surfaces of GRS bridge abutments.