Numerical and Experimental Study of the Unsaturated Hydraulic Behavior of a Railroad Track Profile Considering Fouled Ballast Subjected to Tropical Climate Condition

Environmental actions and geotechnical characteristics are vital in the global behavior of railroad track. Climate, can be crucial to railroad geomaterials behavior, especially in tropical regions. In addition, railroad track behavior depends on water content, retention, and suction pressure over time, being dependent on geotechnical characteristics. These aspects directly influence the amount of water available to infiltrate into the soil, which can percolate or be retained, modifying its water content. Thus, unsaturated soil mechanics should be applied to assess climate-track interaction. This paper evaluated the unsaturated hydraulic response of a railroad track profile in Brazil considering fouled ballast under tropical climate conditions through laboratory tests and numerical simulations. Physical-hydraulic tests were performed with railroad track materials. A numerical FEM model was developed to evaluate the infiltration/suction profile and to quantify drainage, considering laboratory results, distinct fouling levels, and seasons. The results reveal that the hydraulic analysis of the track must consider the unsaturated condition of the materials, which will help to understand the ballast fouling influence on track in terms of hydraulic concerns. Significant suction variation was observed in the subballast when fines are strongly present. Thus, the presence of a fouled layer reduces water transfer to the subgrade due to its water barrier effect. Additionally, in the wet season, suction decreased over the fouled ballast in contrast to the one verified in the dry season. Water balance on the fouled layer surface showed an important amount of runoff, in contrast to the dry period, when a water deficit and high suction values were predominant.