Effect of Gradation and Type of Fouling Material on Drainage Performance of Railway Ballast: A Case Study on AALRT

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Addis Ababa University


A railroad track is a huge structure with different components. Among that ballast is the main structural component used to support the load from railroad ties and to facilitate drainage of water. The drainage efficiency of railway ballast is heavily influenced by aggregate gradations as well as fouling material. It is critical to understand how the gradation of ballast aggregate and fouling material influences railway ballast drainage performance. The main goal of this research is to evaluate the effect of different gradations of ballast aggregate and type of fouling material, and their combined effect on drainage performance of railway ballast on selected sites of Addis Ababa Light Rail Transit (AALRT). In the present study, the hydraulic conductivity of clean as well as fouled ballast specimens are evaluated considering three different American Railway Engineering Maintenance of Association (AREMA) gradation types and about 43 % of three different types of fouling materials. A sieve analysis is conducted to evaluate the gradation and degree of fouling on the track, and the percentage of fouling is also calculated. The hydraulic conductivity of clean and fouled ballast aggregate was then estimated using a constant head permeability test. The Fouling Ratio approach was used to determine the level of fouling at Kality Depot, Transition at Kality, and Gurd Shola. The experimental result of this study revealed that, the extent of fouling at transition is almost reaching to the category of moderately fouled ballast with the value of about 9 %. More uniformity of gradation of clean ballast AREMA No. 3 leads to higher values of hydraulic conductivity than AREMA No. 4 by about 15% and AREMA No. 24 by about 19%. In addition, the clean ballast fouled by clay has shown reduction of hydraulic conductivity by about 4.5 %, 8.5 %, and 32.5 % of AREMA No. 24, AREMA No. 3 and, AREMA No. 4 respectively. It is necessary to create a solution whereby the highway meets the railway line along the transition.



ds: Ballast, Ballast Fouling, Gradation, Drainage, Permeability, Hydraulic Conductivity