BALLAST SELECTION AND GRADING: A SUMMARY REPORT

A recommended procedure for ballast selection and a new grading specification for railway ballast are presented. These recommendations are based on experimental and field results developed over the period 1971-78. The ballast selection procedure offers an improved sequential screening process to eliminate undesirable materials, and permits the classification of surviving ballasts in terms of maximum speed and annual gross tonnage classes. Eleven CP and ten CN ballasts, which were tested during the experimental program, are classified using this system. A broader grading specification is recommended for use in track. This offers significant advantages, especially with top quality ballasts, in terms of resistance to plastic deformation (and thus to differential settlements of track) and superior strength (which improves lateral stability). A complete listing of the Tables of Contents for the annual reports of the project and an explanation of the non-standard ballast classification tests are included as appendices.