On the lateral stability of the sleeper-ballast system

The lateral stability of railway tracks depends on all track components: rails, fastening systems, sleepers, ballast bed and substructure. Among them, the ballast is the weakest one and, due to its granular nature, experimental data obtained in line from full-scale tests, rather than based on analytical formulations, are used to describe its behavior. Until now, several studies have been carried out to quantify the effects of the track-bed geometrical parameters on the transverse strength of the track, but unfortunately not all the possible scenarios have been investigated. To fill this gap, a numerical-experimental research program of in-line tests has been developed in the framework of a cooperation between the Italian State Railways (RFI) and the Department of Industrial Engineering (DII) of the University of Naples Federico II. An ad hoc experimental testing plant, which is able to apply in a more realistic way the testing loads in field conditions, has been designed and realized. In the present paper, the test field is described, and both the features of the new testing plant and the advantages that this new system offers are detailed. Finally, from the analysis of the experimental data obtained from in-line tests carried out on some track panels representative of real scenarios, and with the help of atypical lateral resistance tests, an interesting property is utilized to predict a priori the lateral resistance curves of non tested scenarios.