Investigation of Ballast Degradation on Ethio-Djibouti Railway Line in Ethiopia

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Addis Ababa University


Ballasted tracks are widely used due to their low construction costs, availability of materials, and ease of maintenance. The ballast layer provides resiliency to cyclic loads, drainage, and space for fines accumulation. The primary issue with ballasted tracks is their progressive degradation over time and use. Ballast degradation weakens the interlocking of particles, resulting in insufficient bearing capacity, differential settlements in rail tracks, and obstructing the free drainage of the ballast layer. Understanding the extent to which the ballast bed degrades under cyclic loading enables either standardization or the planning of maintenance schedules. This study was conducted to determine the extent of ballast degradation along the Adama-Miesso section of the Ethiopia-Djibouti railway line following three years of operation. This study collects data on ballast degradation through visual inspections in the field and laboratory tests. Visual inspections were conducted following the severity ranking criteria, which place a premium on the presence of vegetation growth within the ballast. On samples of ballast collected from eight locations along the Adama-Miesso sections, laboratory tests including grading, Los Angeles Abrasion, shape tests (Elongation and Flackiness), specific gravity and absorption, Aggregate Impact Value, and Aggregate Crushing Value were conducted. Gradation was determined by calculating the percentage shift of each PSD curve from the as-built PSD curve limits, as well as Marsal's breakage indices and the material finer than 0.075mm standard sieve size at each location. Additionally, AREMA gradations were compared to the gradations at each location. Mechanical and physical characteristics of the ballast were compared to those of various railway ballast standards. Using Alyamani and Sen's empirical formula, the permeability of the ballast was determined. The investigation discovered that the ballast on the Adama-Miesso section had degraded significantly over three years of operation, necessitating maintenance.



Ballast; Degradation, Investigation, Railway line, Laboratory tests, Field Inspections