0
0
20
20
#7
#7
40
40
60
60
0
0
20
20
#5
#5
40
40
60
60
0
0
20
20
#3
#3
40
40
60
60
0
0
20
20
#1
#1
40
40
60
60
100
80
60
40
20
0
100
80
60
40
20
0
Horizontal Distance (cm)
Horizontal Distance (cm)
e. 20 minutes after T2 began.
f. 6.3 days after T2 began.
Figure 22 (cont'd). Rill profiles.
a. Needle ice on panels before thaw.
b. Melting needle ice
Figure 23. Underside of panels at the end of a freeze.
As thaw continued, the saturated sidewall soil
very early during spring thaw in a temperate cli-
flowed and slid down the rill in variably sized
mate.
soil masses (Fig. 24c) along its entire length, al-
Some of the scattered standing water on the
though especially in mid-rill (Fig. 24b). Tension
soil surface at the beginning of T1 slowly drained
cracks along the rill crests (Fig. 24b) define the
into the thawing soil, contributing to its instabil-
blocks of soil that had begun to slide. The more
ity, and some flowed over the rill crest, transport-
dramatic cross-sectional changes resulting from
ing sediment into the rill. In some locations, the
the rill soil failures occurred at profiles 3 and 5
saturated soil adjacent to, but outside of, the rill
(Fig. 22c and d) in the middle of the bin, rather
flowed over the rill crest into it, forming micro-
than at profiles 1 and 7 near the bin walls where
drainage channels about 1 mm deep along the rill
freezing was less intense.
sidewalls.
24
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