TM 5-822-13/AFJMAN 32-1018
UNCONFINED COMPRESSIVE STRENGTH, PSI
Figure 4-3. Relationship Between Equivalent Cracked Section Modulus and Unconfined Compressive Strength.
soil reaction k. It is to be noted that the relationship shown in figure 4-4 is established based on limited
data. The modulus of soil reaction k can be determined using the plate-bearing test in the field or from table
4-2 when field test results are not available.
Table 4-2. Modulus of Soil Reaction.*
Moisture content percentage
1
5
9
13
17
21
25
to
to
to
to
to
to
to
Over
Type of material
4
8
12
16
20
24
28
28
Silts and clays, LL greater than 50 (OH, CH, MH)
-
175
150
125 1 0 0
50
25
75
150 1 2 5
100
Silts and clays, LL less than 50 (OL, CL, ML)
-
200
75
50
175
250
225
200
150
-
-
Silty and clayey sands (SM and SC)
300
-
300
-
250
-
Sand and gravelly sands (SW and SP)
350
-
-
-
Silty and clayey gravels (GM and GC)
400
350
-
-
-
-
250
300
Gravel and sandy gravels (GW and GP)
500
-
450
-
-
-
-
-
Notes:
1. Values of k shown are typical for materials having dry densities equal to 90 to 95 percent of the maximum. For materials having dry
densities less than 90 percent of the maximum, except that a k of 25 pci will be the minimum used for design.
2. Values shown may be increased slightly if density is greater than 95 percent of the maximum except that a k of 500 pci will be the
maximum used for design.
3. Frost-melting-period k values are given in TM 5-822-5/AFM 88-7, Chap. 3.
*Typical values k in pci for rigid pavement design.
4-5
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