m2/g and a specific gravity of 2.75 g/cm3. This clay
tioning a soil column into 25 segments with ideally
was used in the experiments reported by Nakano and
equal lengths, they serve as an indicator of uniformity in
Tice (1990). For a given dry density ρ and initial water
packing and accuracy in sectioning.
content w0, the exact amounts of oven-dry Morin clay
In Table 1 Tw is the temperature at the warm end of a
and distilled water containing 400 g/g of Br as KBr
soil column while Tc is the temperature at the cold end
were weighed to be packed into a groove. Mixing thor-
of a soil column. For all the experiments, the same lin-
oughly the weighed soil and water, we allowed the
ear temperature field was applied; the duration of ex-
mixture to set for a few days to attain moisture equili-
periments was 22 days. In the last column of Table 1 is
given the concentration of Br in distilled water C0 that
bration. After all four grooves were packed with soil
samples, we bolted together the upper and lower plates
was mixed with dry soil to make the soil columns. In
experiments 14, distilled water without Br was mixed
to seal each of four soil columns with a rectangular
cross section and froze them down to about 15C.
with dry soil, while 400 g/g Br was used in experi-
An experiment began by placing the bolted upper
ments 58. Experiments 14 were conducted to find the
effects of Br on the transport of unfrozen water by com-
and lower plates into the space between the two end
parison with experiments 58, where Br was used.
plates. A stable and linear temperature field was usu-
ally established within 1 hour by adjusting the tem-
The results of experiments 58 are presented in Fig-
ure 2, where nondimensional quantities w+ and C + are
^
peratures of the two baths. After a specified time
passed, the bolted upper and lower plates were brought
defined as
into a coldroom with its temperature being set at
w + = w / w0
10C. The two plates were separated and each sample
(2a)
was quickly sectioned into a total of 25 segments with
C + = C / C0
^
^ ^
equal lengths. Each segment was placed in a glass
(2b)
weighing bottle and oven-dried. The water content and
where w is the measured water (including ice) content at
the dry density of each segment were determined
gravimetrically. The concentration of Br of each seg-
the end of experiments, while w0 is the initial uniform
ment was determined using the Dionex Ion Chroma-
water content. The unit of water content is the weight of
^
water and ice per unit weight of dry soil. C is the mea-
tography Model 2010i.
sured Br content. The unit of Br content is the weight
of Br per unit weight of dry soil.
RESULTS OF EXPERIMENTS
In Figure 2 the nondimensional quantities w+ and
C + are plotted versus the segment number i that is as-
^
The test conditions of the experiments are pre-
sented in Table 1. For all of these experiments, we
signed 125 from the warm end to the cold end. The
aimed to maintain the average dry density of the soil
linear temperature field imposed is also shown in these
figures. The 0C isotherm is located at the interface be-
columns at about 1.45 g/cm3, although the uniform
packing of soil in each column was quite difficult. We
tween segments 10 and 11 so that the temperatures of
examined the uniformity of the soil columns by using
segments 110 are positive while those of segments 11
the measured dry density of all segments after each ex-
25 are negative.
periment. The mean ρa and the standard deviation σ of
It follows from the definitions of eq 2a and 2b that
+ and C + would be one if unfrozen water and Br did
dry density ρ are given in Table 1. Although these val-
^
w
not move at all during the experiments. It is clear
ues are affected by errors associated with rapidly sec-
Table 1. Experimental conditions.
Temperature Temperature
ρa
Experiment w0
gradient
duration
Tw
Tc
C0
(C)
(C)
(C/cm)
σ
(g/g)
no.
(%)
(g/cm)
(days)
1
22.5
1.48
0.13
1.00
1.50
0.120
22
0.0
2
25.0
1.45
0.10
1.00
1.50
0.120
22
0.0
3
27.5
1.46
0.07
1.00
1.50
0.120
22
0.0
4
30.0
1.45
0.12
1.00
1.50
0.120
22
0.0
5
22.5
1.44
0.11
1.00
1.50
0.120
22
400
6
25.0
1.46
0.14
1.00
1.50
0.120
22
400
7
27.5
1.47
0.13
1.00
1.50
0.120
22
400
8
30.0
1.43
0.08
1.00
1.50
0.120
22
400
3
Previous Page
