Evaluation of morphological properties of railway ballast particles by image processing method

The properties of individual ballast particles affect the behavior of ballast layer under train loading. One of the most important individual properties is the morphological characteristics of ballast particles represented by surface texture and angularity. In the present study, the morphological properties of ballast particles are quantified by developing surface texture (ST) index and angularity index (AI) determined on two-dimensional aggregate images. For this purpose, four different types of fresh ballast aggregates (basalt, marl, dolomite and trachyte), rounded river aggregate and degraded ballast sample obtained from railway track are analyzed for each specific sieve size fraction by developed image processing method. Comparison of the developed method in the present study for determination of ST and AI with the previously developed morphological indices shows that there is a reasonable correlation between them. In addition, the results obtained from the air void contents of aggregates in loose condition validate that the developed indices for the evaluation of morphological properties of aggregates can characterize the angularity and surface texture of each individual ballast particle properly.