The Basic Regularities of Acoustic and Elastic Property Changes during
Snow Densification
Anatoly D. Frolov1 and Igor V. Fedyukin1
The structure-texture transformations that occur during dry snow densification and diagenesis cause
changes in acoustic, elastic, strength, thermal, and other properties. The direct experimental study of
these transformations is rather difficult. The acoustic and elastic parameters of snow are very sensi-
tive to structural organization of porous media and can serve as the instrument of their investigation.
In this paper the result of analysis of experimental data on acoustic parameters and dynamic elastic
moduli of dry coherent snow-ice formations in the their whole density range and obtained basic
regularities of its changes during densification are presented and discussed.
As the base of analysis we used the published data of different authors (density of snow from 350 kg/
m3 up to massive ice, 917 kg/m3) as well as our own (snow density from 50 kg/m3 to 500 kg/m3) on
the elastic wave velocities from ultrasonic and seismic field experiments. The tentative analysis of
these data has led us to conclude that snowice formation acoustic property changes in their whole
density range cannot be described satisfactorily by certain smooth functions of porosity (or density ),
including a polynomial of reasonable degree (up to fifth). Our work conception implies first that
during snow densification and metamorphism the changes of it acoustic properties should not be
monotonous in the wide density range. This circumstance reflects the peculiarities of snow medium
structure reorganization. Secondly, that the structure of snow in passing from one transitive state to
another should have one more perfect state with statistically dominant coordination number of medi-
um grain packing corresponding to new space order. We also established that better comparative
parameter, which enables more precisely approximates the laws of acoustic and elastic property
changes, is porosity factor Kp, which we use in our further analysis.
The detailed analysis of experimental data permits us to reveal that there is a set of critical densities:
150, 340, 550, (~710), and 830 kg/m3, at which there are sufficiently abrupt changes of laws of
variations of acoustic parameters and elastic moduli of snow. These critical densities, corresponding
to their porosities, limit the subranges in which a medium structure reorganization is conditioned by
different dominant mechanisms. As obtained by us from analytical modeling, these densities corre-
spond to different values of prevailing coordination numbers of snow-ice medium grain packing: 3,
4, 6, [8)], and 1012, respectively). The empirical equations describing the dependencies of elastic
functions of porosity factor are obtained for five corresponding subranges in the density range from
light snow to massive ice. The conception of transitive states and the data on critical densities are
useful for comprehension of the correct route to study and examination of various snow physical
properties that are necessary to solve some problems of snow hydrology, snow cover dynamics,
melting, etc.
1 Consolidated Scientific Council on Earth Cryology of the Russian Academy of Sciences, Fersman Street 11,
Moscow 117312, Russia
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