Comparative Evaluation of Railway Ballast Degradation

Abstract

Ballast bed is one of the most important components of ballasted railway track system. Over a period of service, it undergoes axial deformation due to the accumulation of train cyclic loading.   However, there has not been a universally accepted method of evaluating ballast degradation, hence, this study focused on comparing two most common methods namely; Marsal breakage ratio  and fouling index (FI). The degraded ballast material was prepared using Los Angeles abrasion (LAA) method at an interval of 250 turns of the LAA test drum, from the fresh ballast to degraded ballast at 2000 turns of the LAA test drum. Series of sieve analysis were conducted and the changes in ballast gradations were evaluated. A strong correlation was observed between the results obtained using the two approaches with a coefficient of determination of 99.24%. Based on the results obtained from the ballast degradation analysis both Marsal’s breakage ratio and the fouling index can be used for the evaluation of ballast degradation. However, Marsal’s breakage index is recommended due to its ability to give the breakdown of the particle size variations.