Figure 6-19. Geotextile Installation at a Bridge Abutment

CEMP-E

TI 850-02

AFMAN 32-1125(I)

1 MARCH 2000

b. Material and Installation Specifications. Geotextiles, and their installation, will conform with the

specifications in chapter 1, part 10 of the AREMA Manual.

c. Design Guidance. TM 5-818-8 will be used for the design of geotextile applications.

d. Drainage Applications. Lighter weight geotextiles are often useful for drainage applications outside of

the track structure, especially in subdrainage.

12. BALLAST.

a. Purpose. Ballast performs four primary functions:

(1) Distributes wheel loads at reduced pressure to the subgrade.

(2) Restrains the track laterally and longitudinally.

(3) Helps maintain track surface.

(4) Allows track structure to drain.

b. Material Type.

(1) As ballast depends on high friction and interlock to be effective in restraining track and must also

withstand large loads, ballast must consist of a hard angular crushed rock or crushed slag.

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