TM 5-822-12
DESIGN OF AGGREGATE SURFACED ROADS AND AIRFIELDS
Group 2. Two-axle trucks.
1. Purpose
Group 3. Three-, four-, and five-axle trucks.
Traffic composition will then be grouped in the following
This manual presents the procedures for design of
categories:
aggregate surfaced roads and airfields.
Traffic composed primarily of
Category I.
2. Scope
passenger cars, panel and pickup trucks (Group 1
vehicles), and containing not more than 1 percent two
This manual presents criteria for determining the
axle trucks (Group 2 vehicles).
thickness, material, and compaction requirements for all
classes of aggregate surfaced roads and for Class I, II,
Category II. Traffic composed primarily of
and III airfields at US Army installations. Road classes
passenger cars, panel and pickup trucks (Group 1
are defined in TM 5-822-2, and airfield classes are
vehicles), and containing as much as 10 percent two-
defined in TM 5-803-4. Class IV Army airfields would
axle trucks (Group 2 vehicles). No trucks having three
normally be paved. Use of the term roads includes
or more axles (Group 3 vehicles) are permitted in this
roads, streets, open storage areas, and parking areas.
category.
Use of the term airfields includes heliports, runways,
taxiways, and parking aprons. Design requirements are
Category III. Traffic containing as much as 15
presented for frost and nonfrost areas.
percent trucks, but with not more than 1 percent of the
total traffic composed of trucks having three or more
3. References
axles (Group 3 vehicles).
Publications cited in this manual are listed in appendix
Category IV. Traffic containing as much as 25
A.
percent trucks, but with not more than 10 percent of the
total traffic composed of trucks having three or more
4. Design of aggregate surfaced roads
axles (Group 3 vehicles).
a. Procedures. The thickness design of aggregate
Category IVA. Traffic containing more than 25
surfaced roads is similar to the design of flexible
percent trucks or more than 10 percent trucks having
pavement roads as contained in TM 5-822-5. This
three or more axles (Group 3 vehicles).
procedure involves assigning a class to the road being
designed based upon the number of vehicles per day. A
d. Tracked vehicles and forklift trucks. Tracked
design category is then assigned to the traffic from
vehicles having gross weights not exceeding 15,000
which a design index is determined. This design index
pounds and forklift trucks having gross weights not
is used with figure 1 to select the thickness (minimum of
exceeding 6,000 pounds may be treated as two-axle
4 inches) of aggregate required above a soil with a
trucks (Group 2 vehicles) in determining the design
given strength expressed in terms of California Bearing
index.
Tracked vehicles having gross weights
Ratio (CBR) for nonfrost areas or in terms of a frost area
exceeding 15,000 pounds but not 40,000 pounds and
soil support index (FASSI) in frost areas.
forklift trucks having gross weights exceeding 6,000
pounds but not 10,000 pounds may be treated as Group
b. Classes of roads. The classes of aggregate
3 vehicles in determining the design index. Traffic
surfaced roads vary from A to G. Selection of the
composed of tracked vehicles exceeding 40,000-pound
proper class depends upon the traffic intensity and is
gross weight and forklift trucks exceeding 10,000-pound
determined from table 1.
gross weight has been divided into the following three
categories:
c. Design index. The design of gravel roads will
be based on a design index, which is an index
Maximum Vehicle Gross Weight, pounds
representing all traffic expected to use the road during
Tracked
Forklift
its life. The design index is based on typical magnitudes
Category
Vehicles
Trucks
and compositions of traffic reduced to equivalents in
V
60,000
15,000
terms of repetitions of an 18,000-pound single-axle,
VI
90,000
20,000
dual-wheel load. For designs involving rubber-tired
VII
120,000
35,000
vehicles, traffic is classified in three groups as follows:
Group 1. Passenger cars and panel and pickup
trucks.
e. Design index. The design index to be used in
designing a gravel road for the usual pneumatic-tired
vehicles will be selected from table 2.
3
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