Ice Strength as a Function of
Hydrostatic Pressure and Temperature
ANATOLY M. FISH AND YURI K. ZARETSKY
performed by Jones (1978, 1982). The studies, car-
INTRODUCTION
ried out over a wide range of constant strain rates
Studies of ice strength in the second half of this
and confining pressures, revealed the anomalous
century have attracted efforts of a number of re-
behavior of ice when its shear strength (at a cer-
searchers. Their attention has been focused on
tain magnitude of confining pressure) reaches a
investigation of ice strength as a function of the
maximum attributable to melting of ice, and then
strain rate, temperature, grain size, and other fac-
gradually decreases with the pressure increase.
tors mainly in simple stress-strain state, uniaxial
Jones showed that the ice strength is a nonlinear
compression. During the last two decades, how-
(power) function of the axial (constant) strain rate
ever, the attention of researchers was shifted to
(see eq 1c below). Further experimental studies
investigation of the mechanical behavior of ice,
with various types of ice revealed effects of tem-
particularly the strength of ice, in a complex stress-
perature, salinity, structure, and other factors on
strain state such as triaxial compression.
the ice strength (Hausler 1983, Nadreau and
In a general case, strength of ice in a multiaxial
Michel 1986, Richter-Menge et al. 1986, Timco and
stress state, when other conditions (the type of
Frederking 1986, Nadreau et al. 1991, Rist and
ice, its structure, the grain size, etc.) are equal, can
Murrell 1994, Gagnon and Gammon 1995, Weiss
be presented as
and Schulson 1995 and others).
At the same time mathematical models were
τ * = τ * (γ i , p, T )
i ˙
(1)
also developed. Thus, Reinicke and Ralston (1977)
i
and Hausler (1986) applied a parabolic equation
where τ * = τ i = J2 = octahedral (peak) shear
i
of Smith (1974), developed originally for rocks, to
stress
describe the strength dependency of ice upon the
J2 = second invariant of the stress devia-
hydrostatic pressure (in our notation):
tor
γ i = octahedral constant shear strain rate
τ * = τ * (p) .
˙
(1a)
i
i
p = I1/3 = hydrostatic pressure
I1 = first invariant of the stress tensor
The absolute magnitudes and the physical mean-
T = ice temperature, K.
ing of the parameters in the Smith equation have
not been defined.
The first studies of the effect of low confining
Nadreau proposed a model (Nadreau and
pressure on creep strength of ice under triaxial
Michel 1986) that described the nonlinear depen-
(σ2 = σ3) compression were carried out by Sayles
dency of ice strength on confining pressure (σ2 =
σ3) by means of a third-order polynominal func-
(1974). The studies showed that the ice strength is
a nonlinear function of the confining pressure.
tion with four phenomenological parameters, to
More detailed investigations of the effect of the
be determined from a series of triaxial tests of ice
strain rate and high confining pressures on the ice
at different strain rates, and the principal param-
strength under triaxial (σ2 = σ3) compression were
eter--the ice melting pressure p*. This pressure
was suggested to be determined either from the
ice state diagram or to be calculated by an empiri-
cal equation.
* Denotes failure stress
Previous Page
