Assessment and Evaluation of Ballast Fouling and Its Effect on Drainage Performance of Ballast; A Case Study on Addis-Djibouti Line

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Addis Ababa University


Railway ballast serves as a major structural and drainage component of railroad track, but during service the ballast layer is subjected to both deformation and degradation due to traffic load. The gradual degradation and deterioration of ballast layer increases the number of finer particles within the track which has an effect on track drainage capacity. The aim of this study is to evaluate the degree of ballast fouling using Void Contamination Index (VCI) on some selected sites of Diredawa, Adigala and Dewanle track sections of Addis-Djibouti railway line. Laboratory tests including specific gravity, gradation, crushing value and Los Angeles Abrasion have been conducted on selected sites. Analytical approach has been used to predict the hydraulic conductivity of fouled ballast. For investigating the influence of degree of fouling on overall hydraulic conductivity of fouled ballast, two dimensional flow has been simulated using a finite element software, SEEP/W. According to VCI values, an average of 30%, 54% and 43% of voids of ballast layer has been filled with fine materials in Diredawa, Adigala and Dewanle track sections respectively. The track drainage capacity in Diredawa is under acceptable drainage category while in Adigala and Dewanie poor drainage category. The results of this study revealed that track maintenance should involve shoulder cleaning of fouled ballast before VCI reaches 35%.



VCI, Ballast fouling, Hydraulic conductivity, SEEP/W