Unsaturated numerical analysis of a railroad track substructure considering climate data

Track substructure materials are mostly in a compacted condition or unsaturated, mainly in tropical regions, characterized by high precipitation and evaporation events. Thus, it is crucial to understand the real impact of climate on track behavior to provide the best design and performance to a railroad, in terms of safety, production, and lower maintenance costs. The main objective of this paper is to evaluate the influence of the water content and suction changes on the hydro-mechanical behavior of a railroad track subgrade considering a tropical climate (southeast of Brazil). Therefore, climate-railroad track substructure interaction was evaluated through numerical analysis (FEM). Geotechnical material parameters were obtained from laboratory tests and from the literature. The numerical model was developed to evaluate water content/suction variation in the subgrade induced by local climatic actions over time. Numerical results were compared with data obtained from suction sensors installed at the subgrade of an experimental track section built in an existing railroad. Water content/suction outputs from the model and field monitoring were applied to resilient modulus tests in laboratory to simulate and to evaluate climate impacts on the subgrade mechanical behavior. The results highlighted the importance of climate aspects to the hydraulic behavior of a railroad track substructure. An important variation of soil suction over time was observed. In addition, suction directly influences the subgrade soil resilient modulus which may contribute to the railroad track geometry deterioration. This paper contributed to provide qualitative and quantitative information about the actual climatic influence on the hydro-mechanical behavior of a railroad track subgrade over time. It could be concluded that climate significantly impacts the hydro-mechanical behavior of the track subgrade, highlighting that the soil studied is not appropriate for the local climatic condition.