Abstract:
Ballast breakage is one of the most critical factors affecting the long-term performance,
stability, and maintenance needs of Sri Lankan railway tracks. The durability
of ballast is strongly governed by its individual particle properties, particularly
size and shape, which control how particles resist compressive stresses and
fracture under loading. However, the influence of these two parameters on breakage
behavior has not been comprehensively studied for ballast aggregates used in
Sri Lankan railway tracks. Consequently, this research presents an experimental
and numerical investigation aimed at quantifying the effects of particle size and
particle shape on the breakage characteristics of railway ballast used in Sri Lanka.
Ballast samples were collected from the Department of Railways, Sri Lanka, and
categorized into four size ranges between 20 and 63 mm. Shape categorization was
carried out using flakiness and sphericity values derived from 3D-scanned particle
geometries. Representative particles from each size and shape group were tested
through single-particle crushing tests under displacement-controlled conditions to
determine peak load capacity, force-displacement response, and tensile strength.
Discrete Element Method (DEM) models of the single-particle crushing test were
developed using 3D-scanned ballast particles and calibrated against laboratory
results to numerically simulate particle breakage. The findings highlight significant
effects of both particle size and shape. Larger particles recorded higher peak
loads but lower tensile strength due to internal flaws and stress concentration,
reflecting a significant impact from particle size. Flaky-shaped particles exhibited
substantially weaker mechanical resistance and more brittle failure modes compared
to cubical-shaped particles of the same size. DEM simulations accurately
reproduced these trends, confirming the dominant influence of size and shape on
particle breakage. Overall, the results emphasize the importance of controlling
both size distribution and shape quality to minimize breakage and improve the
long-term performance of ballast aggregates.
