The Reliability of the Locking Devices of the Switches. Role of the Ballast Bed

The dimensioning of the locking device of a switch is made essentially as a function of the applied loads during the switch rails movement or considering a false route. The phenomena related to the vibrations induced by the track are therefore normally not taken into account. Such vibrations are particularly accentuated by the ballast bed deconsolidation in the sleeper panel supporting the locking device. Unfortunately, there is no specific technical reference in order to control these aspects, even though the most frequent cause of locking device components failures is relied to the vertical oscillations induced by the trains, rather than to the effort to commute the switch rails. In this study, the results of a field investigation carried out at two levels of ballast tamping are reported and discussed. It is found that the ballast compaction plays a fundamental role for the component to be prone to the early attainment of critical mechanical conditions. Procedures for the monitoring of the stability and efficiency of the ballast bed to ensure the required reliability of the locking device are also envisaged.