Environmental conditions

Table 19 (cont'd).

Maximum

Applications to failure (millions)

Water table

Freezing

Freeze/thaw freeze depth

Horizontal strain

Vertical strain

depth

index

events in into subgrade

Asphalt cracking Subgrade rutting

C (F) -days subgrade

Year

m (ft)

(cm)

CEH

AIH-MS11 CEV

AIV-MS1

B. Conventional (F3)

6970

1.5 (4.8)

1191 (2144)

1

13.4

0.46

2.46

0.82

61.97

7071

1.3 (4.2)

1152 (2074)

1

13.4

0.56

2.63

0.47

34.83

7172

1.1 (3.6)

1274 (2294)

1

17.4

0.56

2.53

0.34

26.17

7273

1.2 (4.0)

839 (1510)

0

0.49

1.69

ND

7374

1.3 (4.2)

923 (1661)

2

1.4

0.46

2.04

ND

7475

1.4 (4.6)

968 (1743)

1

5.4

0.49

2.61

1.46

120.66

7576

1.3 (4.2)

931 (1675)

1

0

0.55

2.71

ND

7677

1.6 (5.3)

1256 (2261)

1

25.4

0.43

2.18

0.71

58.36

7778

1.1 (3.7)

1331 (2395)

1

13.4

0.49

2.31

0.51

38.69

7879

1.2 (3.8)

1477 (2658)

1

21.4

0.49

2.72

0.36

27.68

7980

1.2 (3.8)

903 (1625)

1

5.4

0.52

1.87

0.44

33.62

8081

1.2 (4.0)

666 (1199)

0

0.50

1.50

ND

8182

1.8 (6.0)

1227 (2209)

1

29.4

0.42

2.21

0.46

37.95

8283

1.2 (3.9)

589 (1061)

0

0.51

1.34

ND

8384

1.0 (3.3)

1179 (2123)

1

5.4

0.49

1.84

1.18

91.16

8485

1.0 (3.3)

942 (1696)

1

5.4

0.48

1.56

0.98

77.74

8586

1.0 (3.2)

1197 (2154)

1

5.4

0.48

2.70

1.64

ND

8687

0.9 (3.0)

467 (841)

0

0.44

1.45

ND

8788

1.5 (4.8)

898 (1616)

1

9.4

0.45

1.85

0.72

58.30

8889

1.5 (4.9)

1032 (1858)

1

9.4

0.53

1.89

0.45

33.69

8990

1.4 (4.7)

750 (1350)

0

0.55

1.65

ND

Notes:

CEH = Corps of Engineers (horiz.)

CEV = Corps of Engineers (vert.)

AIH-MS11 = Asphalt Institute MS-11

AIV = Asphalt Institute MS-1

ND = no damage

Traffic simulated at rate of 660,000 ESAL applications/yr.

Environmental conditions

termined by this relationship. Figure 27 shows the

The series simulated the 21-yr time period

distribution of estimated water table and freeze in-

196970 to 198990, using a combination of re-

dex for this period.

corded air temperatures and an estimated position

of the water table. The simulations started on 1

Results

October of the first year and proceeded for 365

As in previous simulation series, there was a

days, using mean daily air temperatures recorded

wide variation in the damage amounts predicted

at Buffalo, Minnesota, applied as a step condition

by the different models (Table 19). In general, less

for 24-hr periods. The depth to the water table

damage related to horizontal strain was predicted

was varied based on the total precipitation accu-

in the full-depth design than in the conventional

mulated at St. Cloud, Minnesota, during the thaw

design. On the other hand, when all other condi-

season prior to the simulated freeze season. An

tions are constant, there was more damage related

inverse relationship between precipitation and

to vertical strain in the full-depth design. When

water table depth was applied such that the maxi-

frost did not penetrate the subgrade in the conven-

mum precipitation produced the shallowest water

tional design, essentially no vertical strain dam-

table at 0.91 m (3 ft) below the surface and the

age was predicted.

minimum precipitation produced the deepest wa-

Freeze season characteristics were initially

ter table at 1.82 m (6 ft). The water table was held

quantified by analyzing the total freezing index,

constant throughout the simulation at the depth de-

the number of times that frost was predicted to

39