TM 5-809-12/AFM 88-3, Chap. 15
b. Stationary live loads. Stationary live loads are
pavement design in equation 5-1:
expressed in terms of maximum allowable pounds
per square foot. These loadings are given in table 3-
1. The method used to determine the allowable
(eq 5-1)
1.4
loads is based on the concrete flexural strength, the
1.4
3
h 1.4 & 0.0063
ho '
Ef hs
slab thickness, and the modulus of subgrade
reaction. Entering table 3-1 with the flexural
strength and the slab thickness, the allowable
stationary live load can be selected. Based on the
modulus of subgrade reaction, the load is adjusted
where
using the constant factor given in the note (table 3-
ho = thickness of rigid pavements overlay
1).
required over the stabilized layer, inches
c. Wall loads. Stationary-partition loads are
h = thickness of rigid pavement from design
expressed in terms of pounds per linear foot. These
chart (fig. 5-1) based on k value of
loadings are given in table 3-2. The method used to
unbound material, inches
determine thickness, tc, of the thickened floor slab is
based on the concrete flexural strength, the load,
(as determined by ASTM C 78)
and the modulus of subgrade reaction. Entering
hs = thickness of stabilized layer, inches
table 3-2 with the flexural strength of the concrete
and the load, the concrete thickness is selected,
e. Design Examples. Example design problems
based on a modulus of subgrade reaction of 100 pci.
can be found in appendix C.
The thickness is adjusted using the constant factor
given in the note (table 3-2), for other subgrade
5-3. Subgrade.
moduli.
a. Compaction.
Compaction
improves
d. Design procedures for stabilized foundations.
stabiliity of most subgrade soils and provides a
(1) Soil stabilization or modification. Soils
more uniform foundation for the floor slabs or base
that have been treated with additives such as
course. Method 100 of MIL-STD-621, Compaction
cement, lime, fly ash, or bitumen are considered to
Effort CE 55, should be used to determine the
be either stabilized or modified. A stabilized soil is
compaction characteristics of the subgrade soils.
one that shows improvement in load-carrying
During construction, prolonged exposure of the
capability and durability characteristics. A modified
subgrade to the atmosphere may allow overwetting
soil is one that shows improvement in its
or and drying therefore should not be allowed.
construction characteristics but which does not
b. Cut sections. With the exception of areas of
show an increase in the strength of the soil
special soil, the top 6 inches of subgrade in cut
sufficiently to qualify as a stabilized soil. The
sections should be scarified and moistened to
principal benefits of soil modification or stabilization
approximately optimum moisture content and
include a stable all-weather construction platform
compacted. Cohesive subgrade soils should be
and a reduction of rigid pavement thickness
compacted to a minimum of 90 percent of CE 55
requirements when applicable, swell potential, and
maximum density and cohesionless soils to a
susceptibility to pumping and strength loss due to
minimum percent of CE 55 maximum density.
moisture.
c. Fill sections. With the exception of fill com-
(2) Requirements. The design of the
posed of special soils, all fills composed of cohesive
stabilized or modified layers will follow TM 5-822-
materials should be compacted to minimum of 90
4, and TM 5-818-2/AFM 88-6, Chap. 4. To qualify
percent of CE 55 maximum and all fills composed of
as a stabilized layer, the stabilized material must
cohesionless materials should be compacted to a
meet the unconfined compressive strength and
minimum of 95 percent of CE 55 maximum density.
durability requirements in TM 5-882-4; otherwise,
Some adjustment., for compaction requirements
the layer is considered to be modified.
(3) Thickness design. The thickness require-
may be necessary ;for fills of expansive soils..
ments for a rigid pavement on a modified soil
d. Cut-to-fill sections. When a rigid floor slab is
foundation will be designed as if the layer is
located partially on a fill area and partially on a cut
unbounded using the k value measured on top of the
area, the compaction. requirements set forth in the
modified soil layer. For stabilized soil layers, the
preceding paragraphs should be followed. The
treated layer will be considered to be a low-strength
depth of subgrade compaction in the cut area
base pavement and the thickness determined using
should be increased to 12 inches.
the following modified partially bonded rigid overlay
5-4
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