(lb/in.2 )

(lb/in.2 )

(kPa)

(kPa)

6

106

7 x 10 6

7 x 10 6

10

1206 Unfrozen

3

115 lb/ft

7 x 10 5

5

105

5

108

7 x 10

10

105

Calculated σd (lb/in.2 )

4

7 x 10 4

104

7 x 10 4

10

Density (lb/ft 3)

0.5

1.0

High

114 - 117

4.0

107 - 110

Medium

10

104 - 106

Low

14

3

3

7 x 10 3

3

7 x 10

10

10

100

80

60

40

100

80

60

40

Degree of Saturation (%)

Degree of Saturation (%)

(lb/in.2 )

(kPa)

amount of fines in the material decreases, with the

6

6

10

7 x 10

exception of the class 4 special material. There is

Calculated σd (lb/in.2 )

also a decrease in the slope of the predicted curves

0.5

1.0

with decreasing fine content, indicating the ex-

5

5

7 x 10

10

5.0

pected lesser influence of moisture content on the

9.0

14

moduli of the coarser materials. The curves of the

4

7 x 10 4

two clay subgrades depart somewhat from this

10

pattern. The curve for the 1232 subgrade has an

extremely steep slope, showing a much stronger

10 3

3

7 x 10

influence of the degree of saturation on the modu-

lus. The curve of predicted moduli for the 1206

1232 Unfrozen

subgrade is higher than those for the coarser

2

2

10

7 x 10

100

90

80

70

60

materials. Although this is contrary to conven-

Degree of Saturation (%)

tional rules-of-thumb, high moduli for cohesive

materials have also been reported by Robnet and

Thompson (1973). However, it is more likely that

(lb/in.2 )

(kPa)

6

7 x 106

10

the high 1206 subgrade moduli are related to the

Calculated J 2 / τoct (lb/in.2 )

miscalibration of the testing machine. This possi-

640

bility is being investigated in more detail and find-

330

117

ings will be included in the Phase 2 report (Berg

5

5

58

7 x 10

10

in prep.).

5

For each material tested, Figure 14 shows the

frozen and thawed/unfrozen moduli data points

7 x 104

104

and curves based on the regression equations re-

sulting from this analysis. Data in Figure 14 illus-

trate the rapid increase in modulus as the soils

Class 3 Subbase

7 x 103

103

lus values with decreasing saturation. To illustrate

100

80

60

40

20

Degree of Saturation (%)

these general trends, the calculated relationships

vs. degree of saturation are also shown, for one

stress condition only. As shown in Figure 9, stress

conditions also influence resilient modulus values.

16