Evaluation of the ballast aggregates shape properties using digital image processing techniques

Abstract

The ballast layer is responsible for supporting the railway superstructure, being repeatedly loaded by the traffic. Performance and operation of railway structures can be influenced by ballast aggregates’ shape properties, which include the form itself, angularity and superficial texture. The aggregates shape properties and the particle size may be directly affected by many factors such as: the track usage time, the fouling material that can modify the original granulometry and the maintenance processes. In this context, it is necessary the evaluation of the aggregates’ shape properties aiming to verify how they can influence on railway’s performance and operation. This work measures these aggregates properties collected from quarries (origin) and aggregates collected after some operation time using ABNT, and AREMA standards, as well as the DIP technique. Results indicated that both materials meet ABNT specifications, the same did not happen when AREMA standards were used. Concerning the DIP results, changes were observed on form, sphericity, and superficial texture, caused by structural efforts from the traffic, by the time of operation that produces fine material and, mainly, by the maintenance procedures (tamping).