Table 2. Unconfined compressive strength (MPa) of CFG ice and
natural ice used in this study.
Storage temperature (C)
Storage time
10
15
25
2.16
10.50 1.86
11.58 2.06
1 day
9.12
2.06
10.01 2.65
12.36 0.78
5 days
9.52
2.65
11.67 0.69
10.99 2.35
10 days
9.22
2.55
10.99 0.98
11.87 1.77
20 days
9.61
0.39
Lake ice
1.67
1.18
Pond ice
3.34
maximum axial stress increases with strain rate up to a
Discussion
rate of about 103 sec1. At rates greater than this the
The greater part of the uniaxial unconfined
peak stress tends to remain constant. We therefore
compressive strength data reported in the literature was
believe that the values we obtained for uniaxial strength
obtained using cylindrical samples. Because of the size
are comparable.
of our compacted-snow bricks we chose to prepare
cubical samples for this test series. Kuehn et al. (1992),
using cubes of fine-grained ice (grain sizes about 1
15
mm) ranging in size from 1 to 15 cm on a side, found
that the ductile compressive failure strength is
13
independent of the sample size, at least in the range
11
they used. The strengths they measured were in good
agreement with those of a previous series of tests using
9
similar material in the form of right cylinders. At
10C and a strain rate slightly less than ours, they
7
measured strengths of about 5.4 to 5.9 MPa using cubes
4 cm on a side. We therefore believe that our data can
5
Range of Samples Tested
be compared directly with those of other researchers
3
who used similar test conditions; neither the size nor
5
10
20
1
5
10
20
1
5
10
20
1
(days)
(days)
(days)
the shape of our samples had a significant influence
Storage at 15C
Storage at 25C
Storage at 10C
on their measured strength.
Figure 5. Uniaxial compressive strength of all
It is clear from Table 2 that the uniaxial compressive
samples, showing that there is no convincing evi-
strength of CFG ice is substantially stronger than that
dence of the effect of storage time or temperature
of the natural ice tested. Its strength was not
on the strength of the material.
appreciably affected by either its density or the length
of time elapsed between fabrication and testing.
Figure 5 shows the measured compressive strength
100
Cole (1987)
Schulson (1990)
Schulson and Cannon (1984)
Lachance and Michel (1988)
Camp Century, Greenland
Kovacs (1993)
This Study
10
6 points
19 points
12 points
6 points
1
0
9
1
2
3
4
5
6
7
8
Grain Size, G (mm)
Figure 6. Relationship between grain size and un-
confined compressive strength of ice at 10C and
Figure 7. Mitering jig used for cutting
strain rate of 103 s1. (After Kovacs 1993.)
disks for flexural strength testing.
6
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