Real-time evaluation of railroad ballast condition through change of contact stress using SmartRock

Ballast is a critical part of railroad track for load bearing and drainage as well as offering lateral confinement of the rail ties. It is important to understand the particulate behavior of ballast particles, and have a reliable method or device to assess ballast conditions. In this study, a ballast box test with the full set-up of rail track structure was performed to study the stress change pattern between ballast particles in different ballast conditions such as fouling and shoulder instable, etc. Two new SmartRocks with additional triaxle stress cells were utilized for automatically recording not only accelerations, angular rotations but the measurement of contact stress between SmartRock and ballast particles. The results show that the stress changes are really different in different ballast conditions and SmartRock is capable of automatically detecting ballast fouling and shoulder instability through the change of contact stress.