In response to the increasing structural damage, reduced load-bearing capacity, and diminished durability of heavy-haul railway culverts under heavy axle load transportation conditions, this study focuses on the application of assembled corrugated plates to reinforce diseased culverts. Through engineering applications, numerical simulations, and field tests, the research investigates reinforcement techniques, analyzes parameter influences, and evaluates effectiveness. The results demonstrate that the integration of corrugated plates with existing culverts forms a composite structure, enhancing overall stiffness by sharing loads. Under identical conditions of corrugation height, pitch, and grout layer thickness, arc-shaped corrugated plates exhibit smaller mid-span deflections and stresses compared to triangular and rectangular profiles, with arc-shaped plates showing superior reinforcement performance. The sensitivity analysis results indicate that the waveform is the most sensitive parameter affecting the reinforcement performance. With the waveform fixed, the corrugation height has a relatively significant influence on the reinforcement effectiveness, followed by the corrugation pitch, while the influence of the grout layer thickness is negligible. Field trials on 14 diseased culverts with varying spans demonstrate that corrugated plate reinforcement reduces mid-span deflections and steel reinforcement strains by an average reduction exceeding 40%, with deflection reductions slightly outpacing strain reductions. These findings validate the substantial effectiveness of corrugated plate reinforcement in heavy-haul railway culvert rehabilitation.