APPENDIX D: POSSIBLE INDEX PROPERTIES
ELECTRICAL PROPERTIES
and liquid water content; the effects of sintering
were not directly observed.
Kuroiwa (1962) described an experiment in
The DC conductivity also shows some possi-
which the components of the complex dielectric
bility of being useful as an index property, al-
constants and the AC conductivity of a snow
though it is more sensitive than the properties
sample were measured several times over a pe-
noted above to the presence of impurities in the
riod of 143 hours while the snow sintered at a
snow (Mellor 1977).
temperature of 3C. Over the frequency range
from less than 103 to about 104 Hz the constants
varied significantly and the conductivity increased
ELASTIC WAVE VELOCITY AND
by a factor of 10 during the experiment. The
DYNAMIC ELASTIC MODULI
changes were interpreted as due to the shorten-
ing of the electrical paths because of bond growth
Nakaya (1961) showed that the dynamic
(Fig. D1), suggesting that the AC electrical con-
Young's modulus of processed snow was related
ductivity is sensitive to the bonding and could be
to the bond structure of the snow, and Voitkovsky
a useful index property. In addition, since it is a
et al. (1975) found that the wave propagation ve-
directional property, the AC conductivity may
locity of snow samples undergoing creep defor-
also give information about the degree of anisot-
mation increased with time as the snow density
ropy of the snow. In other work, Keeler (1969a)
and grain contact area increased (Fig. D2). These
found no relationship between the dielectric prop-
erties and the structure of the snow he studied.
0.30
1500
Denoth (1985) found that the static dielectric con-
a.
stants depended strongly on porosity grain shape
410
107
1000
0.20
400
ICE BONDING
390
380
Immediately
after Packing
ρ = 360 kg m3
500
0.10
106
After
143 Hours
0
0
105
2.4
1200
143 hr
b.
2.0
113
70
1.6
800
40
104
1.2
16
0
400
0.8
3 C
ρ = 450 kg m3
0.4
103 2
0
103
104
105
106
0
10
2
4
6
8
Frequency (Hz)
Time (days)
Figure D1. AC conductivity of an aging snow sample as
Figure D2. (A) Creep strain at constant stress and
elastic wave velocity (V) with changing density (ρ),
a function of frequency. Measurements were made at the
indicated elapsed times and the change in structure of the
(B) average grain size (d) and specific grain contact
sample over 143 hours is indicated schematically by the
surface (Sk) as a function of time (t) in days. Measure-
ments of ρ, V, d and Sk were made periodically as a series of
accompanying sketch (from Kuroiwa, in Bader 1962a).
samples deformed at constant stress (from Voitkovsky 1975).
33
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