Investigation on the drainage condition within the ballast layer based on 3D CFD simulations

Abstract

Drainage capability is vital to the performance of ballasted railway tracks. Over the decades, many efforts have been made to develop practical ballast maintenance methods to improve the ballast drainage capability. Although some researchers have attempted to quantify the drainage improvement after a specific maintenance activity, the flow within the ballast lacks thorough understanding. In the study, the effect of five different maintenance activities and the presence of the crosstie on ballast drainage are studied and compared through three-dimensional computational fluid dynamics (CFD) simulations. The five maintenance activities are Cribbing All, Cribbing Interval, Scarifying, Shoulder Cleaning, and Combination. The cleaning profiles of different maintenance activities are based on field practices. The properties of the fouled ballast are derived from the field-collected fouled ballast permeability data to ensure the fidelity of the simulations. Lateral Flow Rate (LaFR) and Longitudinal Flow Rate (LoFR) are introduced to uncover the flow within the ballast layer in both lateral (along with the crosstie) and longitudinal (along with the track) directions. The results suggest that the five maintenance activities affect internal flow characteristics differently. The drainage path within the ballast layer is sensitive to the cleaned volume, and the area, especially the shoulder region is essential for drainage improvement.