Table 20. Midwinter season thaw index summations.
Water table
Freezing
Midwinter thaw index
depth
index
(Total)
(> 30 DD)
C(F)-days
C(F)-days
C(F)-days
Year
m (ft)
6970
1.5 (4.8)
1191 (2144)
25.5 (45.9)
0.0
7071
1.3 (4.2)
1152 (2074)
41.0 (73.8)
0.0
7172
1.1 (3.6)
1274 (2294)
50.0 (90.0)
19.4 (35.0)
7273
1.2 (4.0)
839 (1510)
21.5 (38.7)
0.0
7374
11.3 (4.2)
923 (1661)
56.0 (100.8)
22.3 (40.1)
7475
1.4 (4.6)
968 (1743)
35.0 (63.0)
14.2 (25.5)
7576
11.3 (4.2)
931 (1675)
67.0 (120.6)
20.7 (37.2)
7677
1.6 (5.3)
1256 (2261)
44.0 (79.2)
0.0
7778
1.1 (3.7)
1331 (2395)
26.5 (47.7)
0.0
7879
1.2 (3.8)
1477 (2658)
52.0 (93.6)
18.0 (32.4
7980
1.2 (3.8)
903 (1625)
32.0 (57.6)
0.0
8081
1.2 (4.0)
666 (1199)
41.0 (73.8)
17.5 (31.5)
8182
1.8 (6.0)
1227 (2209)
31.5 (56.7)
21.9 (39.4)
8283
11.2 (3.9)
589 (1061)
92.5 (166.5)
75.0 (135.0)
8384
1.0 (3.3)
1179 (2123)
40.0 (72.0)
34.7 (62.4)
8485
1.0 (3.3)
942 (1696)
40.0 (72.0)
22.9 (41.2)
8586
1.0 (3.2)
1197 (2154)
29.0 (52.2)
0.0
8687
10.9 (3.0)
467 (841)
65.0 (117.0)
40.1 (72.1)
8788
11.5 (4.8)
898 (1616)
79.0 (142.2)
54.2 (97.6)
8889
1.5 (4.9)
1032 (1858)
49.0 (88.2)
0.0
8990
11.4 (4.7)
750 (1350)
70.5 (126.9)
27.0 (48.6)
and the second was a total from only the thaw
curred in the spring, while the remainder occurred
events that exceeded 16C-days (30F-days) (Table
in the winter (Table 21). Horizontal strain damage
20). The quantity 16C-days was chosen based on
in the conventional cross section also occurred
analysis by Mahoney et al. (1985) indicating that
mainly in the spring, with additional significant
pavements approach their critically weak condi-
amounts in both the winter and fall, and very small
tion after this amount of thaw has been experi-
enced. Unfortunately, neither of these quantities
Table 21. Average percentage of total yearly damage
accumulated during four seasons.
parently, a more sophisticated index that perhaps
combines freeze index, severity of midwinter thaw
Accumulated damage (% of total)
events, and other parameters is required to corre-
Section/model
Fall Winter Spring Summer
late with predicted damage.
Conventional
In analyzing the Phase 3 simulation results, we
AIH
22
31
45
2
examined the distribution of predicted damage
AIV
0
40
60
0
through the four seasons defined as follows: fall--
CEV
0
42
58
0
1 October to start of freeze, winter--freeze season
Full depth
as defined by freezing index, spring--75 days fol-
AIH
16
51
32
1
lowing end of freeze season, summer--remainder
of 365-day simulation. The simulations predicted
AIV
2
44
16
38
CEV
0
80
20
0
a wide variation in seasonal damage amounts for
different years, especially in the vertical strain dam-
Notes:
age in the conventional cross section (Fig. 30). In
AIH = Asphalt Institute horizontal (MS-11)
years when vertical strain damage was predicted
AIV = Asphalt Institute vertical (MS-1)
for the conventional cross section, a majority oc-
CEV = Corps of Engineers vertical
41
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