For which sleeper type is sand commonly used as ballast (especially in arid areas or light-duty track)?

Introduction / Context:
Ballast characteristics affect drainage, interlock, and track resilience. While broken stone is standard, sand ballast has been used on certain routes, particularly in desert or low-axle-load conditions, and with specific sleeper types.

Given Data / Assumptions:

• Historical Indian practice where cast-iron (CI) pot or plate sleepers have been used.
• Light to moderate traffic contexts; arid zones with abundant sand.

Concept / Approach:

CI sleepers, with their seat geometry and bearing characteristics, can work with sand ballast where interlocking requirements are modest. Wooden and steel sleepers generally prefer angular stone for adequate lateral resistance and drainage; sand lacks the shear interlock and can migrate.

Step-by-Step Solution:

Verification / Alternative check:

Older permanent-way manuals and case studies in desert sections document use of sand ballast with CI sleepers.

Why Other Options Are Wrong:

Wood and steel sleepers generally require crushed stone for stability; “all equally” is not true; “none” ignores documented practice.

Common Pitfalls:

Assuming sand performs like broken stone; overlooking drainage and fouling issues with fine materials.

Final Answer:

Cast-iron sleepers