Question

Need help with a correct answer! Of the five ballast functions numerically listed, which two in your opinion might be the most important and briefly explain your reasoning.

1. Resist applied loads (vertical, lateral, and longitudinal) to maintain track position.
2. Provide positive and rapid drainage of water.

3. Accommodate track surfacing and alignment maintenance.

4. Provide resilience needed to dissipate large and dynamic loads.

5. Provide adequate void space for storage of ballast-fouling material
without interfering with ballast particle contact.

Answer 1

Options 2 and 4 are correct. Main function of ballast is to provide drainage of water and to spread load from sleepers to subgrade. It provides resilence needed to dissipate large and dynamic loads. Option 1 is not an important function of ballast as ballast itself cannot resist much of applied loads however it distributes loads coming from the sleepers into subgrade and holds sleepers into position. Option 3 i.e. accomodate surfacing and alignment maintainance can not be maintained alone by ballast but it can act as support to the superstructure through sleepers.