ture is estimated to be 291 MN or ≈ 3.24
200
MN/m. Since most estimates for the in
TF = 2 θ 0.505
tegrated limiting pack ice force lie be
160
tween 104 and 105 N/m (Parmerter and
Coon 1973, Rothrock 1975, Hibler 1980,
Nevel 1983 and Croasdale 1984), the
120
pack ice driving force would seem to be
the design limitingforce load. However,
80
since the pack ice driving force can be
t
θ = ∫o (Tw Ta ) dt
distributed across a floe that is much
t = Time (days)
wider than the structure, the concen
Tw = Seawater Freezing Temp.
40
Ta = Mean Daily Air Temp. < Tw
trated force at the structure can easily
exceed the stress required to fail the ice.
Therefore, for this model and no other
0
1000
2000
3000
4000
5000
factors being considered, the design
θ, Cumulative C Freezing Degreedays After Ice Formation
force would be the calculated value.
Figure 27. Seaice thickness vs. seawater freezing degreedays after
The constants given in eq 15 and 16
a stable ice cover has formed.
are best estimates and may need to be
revised (Sanderson 1988). The estimated
force of 291 MN is considered an upper limit for
sheet is estimated to be 5.15‰. We assume the ice
the conditions given. Indeed, for a similar ice sheet
sheet has an average temperature of
10C. This is a reasonable value for cold, late
thickness and structure width, the ice force devel
oped against the structure due to nonsimultaneous
winter firstyear sea ice along the Alaska Beaufort
ice crushing failure appears to be less than half
Sea coast. The bulk porosity is found to be 52.20‰

from the equation, φB = 19.37 + 36.18 S B.91 Ta 0.69 ,
0
the above calculated indentation force (Wright
and Timco 1994).
given in Figure 13a.
The peak failure stress in sea ice occurs at a
strain rate of about 103s1 for smallscale ice
SUMMARY
samples with an aspect ratio less than 2. As the
sample size or the volume of ice under load in
A constitutive relationship, in the form
creases, the peak stress occurs at a lower strain
σc = B2 εl/n φm , was developed for predicting the
˙
rate (Sanderson 1988, Gavrilo 1995). At fullscale
B
unconfined compressive strength of firstyear sea
ice structure interaction when the aspect ratio is
ice floes as a function of only two parameters, the
greater than 50, the peak stress appears to occur
at an effective strain rate εe around 105 s1. Since
applied strain rate and the ice floe bulk porosity.
˙
This equation was evaluated using full seaice
the structure width d is very much greater than
sheet thickness, horizontal unconfined compres
TF, plane stress conditions apply and the appar
sion test data, so no uncertain small to large
ent ice sheet velocity V at this strain rate is