TM 5-628/AFR 91-44
CHAPTER 4
BALLAST
4-1. General. Ballast is a select material placed on
(1) Size and gradation.
the subgrade to:
(2) Shape (angularity).
a. Restrain the track laterally, longitudinally,
(3) Weight.
and vertically under the dynamic loads imposed by
(4) Strength.
trains and the thermal stresses induced in the rails by
(5) Durability.
changing temperature.
(6) Cleanliness.
(7) Economics.
c. Distribute the load of the track and trains to
b. New ballast materials used in the maintenance
prevent overstressing the subgrade.
of Army track shall meet the requirements specified
in the AREA Manual For Railway Engineering,
chapter 1, part 2, for the gradation requirements
4-2. Selection criteria.
given in table 4-1.
a. Considerations for selecting materials to be
used as ballast include:
b. During major maintenance or track rehabili-
4-3. Maintenance.
tation, dirty or fouled crushed stone or slag ballast
meeting the requirements of paragraph 4-2b may be
draining, and free of vegetation, soil (mud), and
cleaned or reconditioned and reused.
other foreign materials.
c. Ballast materials shall not be allowed to
cover or be at a level above the top of the ties.
4-1
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