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Mechanical and structural properties of ice
Ruedy, R. R.
DIVISION OF BUILDING RESEARCH
MECHANICAL AND STRUCTURAL PROPERTIES OF ICE Two literature reviews prepared by R. R. Ruedy
during an investigation of the properties of ice carried out in 1943 under the direction of the
National Research Council of Canada
Internal Report No. 395 of the
Division of Building Research
Ottawa February 1972
The possibility of major oil and gas developments in Northern Canada, particularly in offshore areas, has brought about an increased
interest in the behaviour and properties of ice. This interest is not
confined to the forces that ice covers might exert on structures,
al-though this is a major problem. Ice covers can also be used as
sur-faces for roads and airstrips, and consideration is being given to their use as platforms for drilling operations.
In 1943 the National Research Council of Canada undertook, with the assistance of several university and other groups. a major
investigation of the properties of natural and reinforced ice. At the
conclusion of the war the information obtained in this study was assembled
in the Council's files. Some of it is relevant to current interests and
needs, and it was decided to make it available for limited distribution in the Internal Report Series of the Division of Building Research.
The present report contains two literature reviews prepared by R. R. Ruedy, who was a member of the staff of the National Research
Council. The first is on the mechanical properties of ice, and considers
Young's modulus and strength. Several topics are considered in the
second review, including effect of salts, properties of sea ice. viscosity
and plasticity of ice and aspects of ice engineering. These are presented
just as they were prepared in 1943, without revision. They still form
an excellent starting point for a study of the subject, to be updated as required by the reader through reference to more recent literature.
Also included in the report. as Appendix A, is a summary of selected technical data on ice obtained from the investigations and
thought to be of current interest. Further selections will be made for
reproduction in subsequent reports.
Many individuals participated in the field and laboratory research
associated with this wartime activity. The Division of Building Research
is honoured to have this opportunity to make the fruits of their efforts available for application to present-day problems of national concern.
Ottawa
February 1972
N. B. Hutcheon, Director
Page
PART I. MECHANICAL PROPERTIES OF ICE
Introduction
Young's Modulus for Ice
1
1
3
(a) General Features 3
(b) Young's Modulus from Compression Tests
between the Freezing Point and Zero Degrees.
Progressive Loading. 3
(c) Young's Modulus for Bending Stresses
(Progressive Loading) 5
(d) Young's Modulus for Decreasing Loads in
Bending Tests on Beams of Ice Prepared
from Frozen Snow 5
(e) Young's Modulus from the Velocity of Sound
in Ice (Adiabatic Value) 7
{f} Miscellaneous Values for E 7
(g) Rigidity of Ice and Poiaaonts Ratio 7
Strength at Failure
{a} General Features
(b) Crushing Strength of Ice
(c) Tensile Strength of Ice
(d) Strength of Ice in Bending Impact Strength of Ice
(a) Strength in Sudden Loading (b) Shifting Loads (c) Impact Strength 8 8 9 10 11 12 12 13 13
PART II. STRUCTURAL PROPERTIES OF ICE Effect of Salts
The Production of Large Single Crystals Heat Conductivity
Ultimate Strength of Ice in Shearing Internal Friction (Viscosity) of Ice
Experimental Work on the Adhesion of Ice Ice Floes as Landing Fields for Aircraft Properties of Sea Ice
Ice in Excavation of Shafts and Tunnels Reinforced Ice as Structural Material Coefficient of Linear Expansion of Ice Temporary Supports of Ice
Ice as a Building Material
Destruction of Ice Masses by Explosions Plasticity of Ice References Appendix A 15 18 19 20 21 21 24 28
29
32 33 33 34 34 35 39Note: The material in this report refers to a small number of tests and the results cited are not to be taken as average values.
Ice differs in several respects fr orn other rna te r ial s of COITlITlon
occurrence. Metals and stones are aggregates of s rria lI grains. and
SOITle of their properties differ quite rna r kedly f'r orn those of single crys-tals of the s arn e rna te r iaI, Ice. whether gathered fr orn lakes and rivers or produced artificially, consists of a few large crystals. and the prop-erties of ice consisting of rrrinute grains ar e only irnp e rf ec tly known fr orn
studies on glaciers and scattered tests on icicles and snow. The question
of grain size that plays such a large part in m.eta.Hur gy, creates therefore
little difficulty in the study of blocks of ice.
When ice grows undisturbed on the surface of large water bodies or in srna.Il vessels. the optic axis or axis of the hexagonal p risrri, is
always perpendicular to the surface of the ice-cover, except near the
edges and in the first stages of freezing. As a result of the presence of
large single crystals of the hexagonal sys tern, the properties of ice depend
on the direction considered, in particular on the direction parallel to the
base of the p risrn, or parallel to the sides of the prism, that is. parallel
to the optic axis and the direction of undisturbed growth. Roughly
speak-ing crystals of ice behave as if they were built up of an infinite numb e r of
very thin sheets of paper fastened together with SOITle viscous substance that allows the sheets to slide over each other when strong forces are applied parallel to the sheets, or in other words, perpendicular to the
optic axis. The single sheets are nearly inextensible and quite flexible.
On account of the iITlperfect c ementa tion of the sheet, displ.ac ement s in
the fo r m of punching are readily produced parallel to the base. When,
for instance. bars of square cross-section (1 sq. CITl.) with the optical axis parallel to the length of the bar, are placed upon wooden supports, and a cord carrying a weight of about 5 kgrn , is slung around the section between the supports, a piece corresponding to the thickness of the cord
is gradually pushed downwards. No cracks occur in the bar, but the
dis-placed piece is streaked with fine lines parallel to the base of the
hexag-onal crystal. On the other hand. since the crystal planes ar e flexible. a
rod will bend under its own weight when the optic axis is perpendicular to
the length of the bar and the sheets of paper are horizontal, but if the bar
be turned over so that the basal planes are vertical. the rod is rn o r e dif-ficult to bend even when loads are applied.
Another irnpor tant difference between ice and COITlITlon engineering rna te r Ial s is that stones and rn e ta.l s are used at a ternp er a tur e farther
be-low their melting and softening points than ice ever is out of doors. Ice.
therefore, is in an even less stable state than rne ta l s and stones are. and the ternper a tur e must be expected to exert a strong influence upon its
rne chanical properties. This variability is enhanced by the peculiar
Melting Point of Ice at Various Pressures
Temperature
I
Pressure TeITlperature Pressureof °e *kgITl. per
I
lb. per of °eｾＧ＼ｫｧｉｔｬＮ
perI
lb. perI • I .
sq. CITl.
!
sq. rn, sq. CITl. , sq. In.I 32 0 1
!
14 -12.5 1410 II, 20, 064 2.5 336 4, 781 5 -15.0 1625 23, 124 23 5 615 I 8,751 -17.5 1835 26, 112I
- 7.5 890 112, 665 -4 -20.0 2042 29, 058 I 14 -10 1155 :16,436 -22. 1 2200 31, 306I
I
At terrrpe r a tu r e s not rnuc h below freezing a relatively s rriaII pressure
would be sufficient to rn eIt the ice at the points of greatest pressure. The
foot of a c ol urrm or pile of ice, 15 rnetr e s to 20 rn e tr e s high, ought to show signs of m el ting even though the whole c ol urnn is at a terrrpe r a tu r e a few
degrees below freezing. A few towers of ice of this height have been built
as showpieces, but the walls were rria d e 33 inches thick and the base offered a large resistance to flow and gliding.
The general rn ec harric a l strength of ice is Lirnite d by another property
of the point of fusion of ice. When pressure is applied to ice that is colder
than -200
e
or -30o
e
and therefore much stronger than ice near thefreez-ing point, and the pressure is increased to 2, 250 kgm, per sq. CITl. on all
sides, new fo r rn s of denser ice form., narn e ly Ice III (at ternpe r a tur e s
be-tween -30° and -50o e ) and Ice
IJ..
slightly denser than ice III (between -700 eand -30° e). On account of these tr an sf or rnations the resistance and
ex-pansive force of ice is Hrni.ted; the pressure exerted by ice cannot exceed
about 2, 500 kgrn, (35,560 lb. per sq. in.), since at this pressure occurs
the change to denser fo r m s , At very low temperatures Ice
m
and Ice IIare obtained at ordinary pressure, and on wa r m.ing Ice III fr orn the
teITlper-atures of liquid air to -130° C it is tr an sfo r m ed into ordinary ice as shown
by the change of the c ornpact pieces into a fine rn ea l of considerable v oIurn.e ,
Only ordinary ice shows a lowering of the rn e l ti.ng point by increase
in pressure. Above the freezing point, water can be kept solid by raising
the pressure to 6, 300 kgrn , per sq. crn , and by increasing the pressure by
about I, 000 kgrn, per sq. CITl. for each increase of 5 ° e in temperature.
YOUNGS MODULUS FOR ICE
(a) General Features
On account of the card-pack structure of single ice crystals, ice
is not elastic except for extremely small and unimportant loads. With
ice, the value of Youngt s modulus depends on the successive increments
of load; furthermore, the deformation under any load increases as the
loading is sustained, and Young! s modulus decreases in proportion. To
render measurements by different workers comparable, a standard method
of loading would have to be adopted. At present results are available for
loads of very short duration, for loads applied for a few seconds and in-creased step by step, for decreasing loads, and for loads sustained for hours or days.
In general, when a cube of ice of about 5 -inch side length is loaded
for the first time at 280F with 10 lb. per sq. in. and the load normal to
the optic axis is sustained for not more than five minutes, there is
com-plete recovery on removal of the load. After the first and second
re-petition of the test, and also when the first period of loading is lengthened,
recovery is not complete. About 40 per cent of the total change in length,
25 millionth of an inch per inch length for a load of 10 lb. per sq. in.,
re-mains when the load is removed. A permanent set in the same ratio is found
when loads of 20 or 30 lb. per sq. in. are applied. When a load of 20 lb.
per sq. in. is allowed to act upon the block, the block yields continuously for about 3 hours 30 minutes and retains 90 per cent of its deformation when the load is removed (total elongation 250 millionth inch per inch
length). Different values are found for other loads (Brown).
Progressive deformation is also found with rods of ice prepared by freezing snow mixed with water and consisting of coarse grains rather than
large crystals. When such a rod, 14 crri, long and 6 sq. crn , in
cross-section is subjected to a compression or a tension lasting for about two months, the load being 2 kgrn , per sq. crn , , the average temperature _50 C (23 ° F), the rod increases 0.74% in length in 30 days when tension is applied,
and decreases 0.37% in length when compressed. When the applied pressure
is varied, the shortening in compression is proportional to the pressure (0.007% per day for 1 kgrn, per sq. crn , , 0.015% for 2 k grn , per sq. c m , ] provided that the pressure does not exceed about 4 kgrn , per sq. ern, at
-5°C (23°F). At 5 kgrn , per sq. ern, the reduction in length is 0.11%
(Haefeli).
(b) Young's Modulus from Compression Tests between the Freezing Point
and Zero Degrees. Progressive Loading.
River ice, free from flaws, cracks, air bubbles or foreign material,
was cut into cubes of 5 inches by 5 inches by 5 inches, or into prisms 5
inches by 5 inches by 10 inches. The loads were applied normally to the
160 seconds until the
Several tests were carried by 250 lb. at the end of either 5, 10, 20, 40, 80 and
total load amounted to several thousand pounds. out at each loading rate.
Results are shown in the following table for the temperatures 28° F, 14°F and 3°F, for the intervals corresponding to an increase of 1,000 lb. of loading.
Young's Modulus E at various rates of loading
(Compression at _2°, _8° and -16°C)
IncremJnts
(40 lb. per 1 st 2nd 3rd 4th 5th 6th
sq. in.)
Young! s modulus in
roo,
000 lb. per sq. in.Temper-ature ° F 28 18 3 28 18 3 28 18 3 28 18 3 28 18 3 28 18 3 Rate of loading: 5 sec. 9.5 10.3 7.2 8. 7 9.3 5 7.7 8.3 3.7 6. 8 7. 3 2.8 5.3 6. 3 2 3. 1 4.3 10 sec. 8 5.8 4 2.8 2 20 sec. 6 11 3.6 7 2.3 5. 1 1.6 3.8 1 2. 8 2.2 80 I sec. 7 4.3 1.1 3.2 2.7 2.3 2 160 sec. 5.3 2.8 1.8 1.3 1 320 sec. 5 2.8 1.9 1.5 1
The results show that the value of Youngt s modulus is progressively
lower as the duration of loading increases, and as the actual load increases. Furthermore, the corresponding values of the modulus are higher
at lower temperature. The difference tends to increase at each repetition.
The values of Young! s modulus at 14 ° F for loadings five seconds
apart differ but slightly from the values obtained at 3 ° F when the rate of loading is correspondingly decreased; thus the curve for a loading rate of
160 seconds at 14°F is a Irn o st the same as that for the loading rate of 320
(c) Young's Modulus for Bending Stresses (Progressive Loading)
The beams tested were 3 inches wide by 2 inches deep, and the
span was 41 inches. The load was applied in increments of one pound
at each of two loading sections, 14 inches from the supports. The
de-flection was read 5 seconds later and the load increased by one pound
1m
other tests the loading intervals were 10 seconds, 20 or 40 seconds.One series of experiments was carried out at approximately 14° F, the other at 28° F.
Young! s Modulus (lb. per sq. in. ) Axis of c r ys tals horizontal Axis of crystals vertical Temperature One pound loads added at intervals of 5 sec. 10 sec. 20 sec. 40 sec. 790, 000 610,000 450, 000 355, 000 844, 000 681, 000 625, 000 615, 000 674, 000 751, 000 661, 000 441, 000 80 8, 000 753, 000 653, 000 742, 000
In all the tests, the value of Youngts modulus decreases in successive
stages of loading, and with increased duration of loading at each stage. The
value of the modulus is greater at the lower temperature. It is slightly
greater when the crystals are vertical than when they are horizontal (Brown)
with the optic axis parallel to the bar (average ratio 1. 15 and 1. 07);
com-parison of the results is difficult, however, because the depth varied from beam to beam.
(d) Young's Modulus for Decreasing Loads in Bending Tests on Beams
of Ice Prepared from Frozen Snow
The bars used were about 250 rnrn , long, 15 rnrn , wide and 15 rrirri ,
deep. The optical axis, or the direction of freezing, was either parallel
or perpendicular to one pair of side surfaces, and by merely turning the rod through 90° about its long axis, the behaviour in two different directions perpendicular to the optical axis could be studied; in one direction the
crystal base planes would be parallel for single crystals, in the other
orien-tation they were perpendicular to the direction of the force. In order to
reduce deformations, no deflection was allowed to exceed 0.15 rnrri , at the centre of the beam.
Each b earn was subjected to five or six cycles of loading and un
loading before m ea s ur ernen ts were started. Readings were then taken
while the bar was unloaded in steps of about
i
kgrn , at a tirne , There-rnova l of the load took about one second at each step.
Young's modulus in kgrn, per sq.ITlITl. at decreasing loads
in bending near the freezing point
(i) Long axis of bar parallel to optical axis
Load 1. 04 0.74 0.54 0.24
kgrn, kgrn , kgrn , kgrn . Average
Fir st rod, first position 948.3 920.4 931. 0 953.5 938.3
second position 960.4 944.3 951. 7 924.8 945.3
Second rod, first position 934.3 935.5 940.4 958. 1 942. 1
second position 935.3 944.8 945.7 951. 7 944.4
Third rod. first position 971. 1 949.8 979.8 (1012.0) 978.1
second position 954.4 975.7 970.6 976.6 969.3
Average of these and other tests 957.6
(ii) Long axis of bar perpendicular to optic axis
First rod Second rod 1131 1124 1134 1111 1106 1126 1116. 6 1121. 1
Average of these and other tests 1120.3
The rn ea s ur errierrts at decreasing loads give for stresses parallel to the optic axis a value of
= E o
=
95.760 kgm. per sq. ern. (13.6 x 10 5 lb. per sq. inv ) 112, 030 ｫｾｉｔｬＮ per sq. CITl. (15.9 x 10 lb. per sq. in.) = 1. 17for stresses perpendicular to the optic axis. after repeated stressing and at ternpe r a.tur e s a few degrees below freezing.
(e) Young's Modulus from the Velocity of Sound in ice (Adiabatic Value).
The difficulties that the progressive yielding of ice in all except the slightest stresses creates for the determination of Young" s modulus are avoided by methods depending on the velocity of sound or of high
frequency vibrations, or impulses (Brockamp and Mothes; Boyle and
Sproule). The testing forces are small and change very quickly. Using
frequencies between 7 and 13 kilocycles per second and rods in which
the optical axis is parallel to the greatest length, the results are as
follows:
Young! s Modulus
Temperature of lb. per sq. in. kgrn . per sq. ern.
°c
14 1. 375 x 10
6
96, 700 - 10- 22 1. 48 x 10 6 104, 000 - 30
- 31 1. 58 x 10
6
111, 000 - 35Seismic methods applied to a glacier gave E
=
71, 000 k grn , per sq.em. near the freezing point (Brockamp and Mothes). (f) Miscellaneous Values for E
Russian engineering articles use the following average values for Young's modulus in compression, bending, and tension:
30, 000 kgm. per sq. em. (Komarovskii)
30, 000 to 50, 000 kgm. per sq. em. according to the temperature (Bernstein).
(g) Rigidity of Ice and Pois sonts Ratio
The modulus of rigidity is determined from the twisting of cylinders
about the long axis of figure, or from the propagation of high frequencies in
rods of ice. The optic axis of the crystals may be parallel (N ) or
perpen-dicular to the length of the cylinder (N
9 0). 0
Temperature, o C N
o N9 0 ton per sq. em. and per
radian 29.4 27.2 10 17 about 0
o
- 5 Koch Weinberg Weinberg (both 1938) ＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭＭ｟ｾＭThe propagation of sound gives a much larger value N
=
91. 7, atbrass tubes (Ewing, Crary, and Thorne). Seismic methods of wave
propagation give N
=
26, 100 kgm. per sq. ern. for ice contained ina glacier (Brockamp and Mothes).
The ratio between Young! s modulus and the modulus of rigidity is 0.361 for glacier ice (Brockamp and Mothes), and 0.365 for high fre-quency sounds (Ewing et al ).
STRENGTH AT F AlLURE
(a) General Features
In order to derive practical values for the strength in crushing, bending, tension, cutting and twisting, an attempt has been made to
collect the results of all the tests made up to 1936 and to take the average.
The result is as follows (B. P. Weinberg, 1936).
Number of tests on the strength of ice
Nurnbe r of tests Average strength kgrn , per sq. ern. in USSR before 1918 1918-1936 in other countries before 19181918-1936 Total Crushing 43 75 279 72 32 458 Bending 17 345 346 44 66 801 Tension 11 10 63 27 5 105 Cutting 7 0 62 13 10 85 Torsion 4 9 0 0 0 9 Total 439 750 156 113 1458
Only about half of these measurements were made in a methodical
fashion, the remainder were more or less casual observations so that the
meaning of the average remains doubtful. Thus if, the group of readings
obtained in crushing tests made under comparable conditions (281 determinations) and the corresponding bending tests (430 determinations) are arranged in ten groups of 28 tests (respectively 43 tests), in the order of increasing strength, and the average strength in each group is expressed in percentage of the sum of all the loadings, the result is as follows:
Distribution of Results Nurnb e r of gr oup of
8 9 10
tenths of total number 1 2 3 4 5 6 7
Average strength in
0/0
of total load used in
crushing 45 57 64 79 88 99 I I I 123 139 195
These results show that readings lower than the arithmetic average are more frequent than readings greater than the average, in the ratio of
about 3:2, and suggest that owing to the experimental difficulties, the
number of measurements made under comparable conditions is not sufficiently great to lead to a satisfactory average.
(b) Crushing Strength of Ice
To obtain characteristic compression fractures, the load must be
applied rapidly, although without shocks, so that the ice has no opportunity to flow or to change.
When the rate of loading is such that 40 lb. per sq. in. is added every other second, the crushing strength of 5 -inch cubes taken from the St. Lawrence river is as follows:
Crushing strength
Temperature OF lb. per sq. in. k grn , per sq. c rn , °C
28 300 21.1 2.2
14 693 48.7 - 10. 0
2 811 57 - 16. 7
There appears to be little difference in strength at failure whether the load be normal to the crystal basis or perpendicular to the optic axis
(Brown). When the loading rate is only 8 lb. per sec. the cubes have time
to change shape before they break.
Tests on artificial ice, prepared either by placing distilled water
or mixtures of powdered ice and water, in a refrigerator, were carried
out in standard testing machines, using ice cubes of 7 c rn , side. The load
was increased at the rate of 3 kgm. per sq. crn , per second (42.7 lb. per
sq. in. per sec). At a temperature of - 8°C (18°F) the strength in
com-pression in three series of tests was as follows (Romanowicz and Honigmann).
or 40.0 569 43.0 612 44. 1 627 k grn , per sq. c rn , at 80 C lb. per sq. in. at 180 F
The highest reading obtained was 54.4 kgm., the lowest 34 kgm. per sq. c rn , When the five-inch cubes used for compression tests are quite
clear, so that ordinary print can be easily read through them, the first
outward signs of yielding at temperatures of 280 F to 300 F occur at loads
from 100 to 200 lb. per sq. in. A slight noise is heard, and one or more
spots of a slaky appearance develop in the block. These regions spread
gradually through the block, and the ice is then no longer transparent.
At ternpe r a.tur e s between 140
F and 16° F and loading intervals of
5 sec. and 10 sec., the blocks remain clear even when the rna xirnum
the ice become clouded faintly and fairly uniformly as a rule. At the slower rates of loading, however, the blocks become clouded.
At 3°F the loads had to be added at intervals of 160 seconds to
produce loss of transparency.
That the temperature has a considerable influence upon the crush-ing strength is also shown by measurements by Witman and Shand r i.kov ,
Relation between crushing strength and temperature
Temperature OF lb. per sq. in. kgrn , per sq. crn , °C Ratios
23 220.5 15. 5 -5 1 14 253.2 17.8 -10 1. 20 5 354. 1 24.9 -15 1. 61 -4 394.0 27.7 -20 1. 80 -13 487.8 34.3 -25 2.20 -22 506.3 35. 6 -30 2.30 -31 583. 1 41 -35 2.65 -40 615.4 43.2 -40 2.80 -49 665.6 46.8 -45 3.02 -59 694. 1 48.8 -50 3. 15 -64 725.4 51.0 -55 3.30 -73 778.0 54.7 -60 3. 53 (c) Tensile Strength of Ic e
Only a few determinations of the tensile strength of ice are avail-able (Romanowicz and Honigmann; Bernstein).
At an average temperature of -8 ° C (18° F) the tensile strength,
measured in a standard testing device for concrete on cylindrical pieces of artificial ice was as follows when the load was increased at the rate of
O. 1 kgrn, per sq. ern, per sec. (or 1.42 lb. per sq. in. per sec. )
16. 1 229 18.3 260 17. 7 k grn ,per sq. em. 252 lb. per sq. in.
The highest reading in three series of measurements was 24.8 kgrn , ,
the lowest 14.8 kgm. per sq. crn ,
The tensile strength of ice is therefore less than half the crushing strength of ice at the same temperature and forms a limit that has to be considered in all cases of more complex stress distribution.
Tests with natural icicles shaped into cylinders gave a tensile str ength of
10.3 kgrn , per sq. crn , at - 2.4 °C (146.5 lb. per sq. in. at 28°F)
The c r o s s - section of the test pieces measured 2 to 7 sq. c rn , , the height
3.3 to 4.9 crn , The ice was coar se - grained (Haefeli).
(d) Strength of Ice in Bending
The beams of St. Lawrence river ice used in the bending tests were
loaded step by step until they broke. All the beams broke suddenly at or
near the loading point. Tests were made with crystals either horizontal
or vertical, either at 28°F or at l4°F (Brown). Strength in bending (lb. per sq. in. )
(Modulus of rupture) Axis of crystals horizontal Axis of crystals vertical Temperature Ra te of loadmg: 5 sec. 10 sec. 20 sec. 40 sec. 178 173 134 141 232 217 228 281 28° to 30 ° F 170 170 243 ? 152 191 216 208 240
The average modulus of rupture for 21 beams tested at 28°F to 30°F
was 171 lb. per sq.i.n , , which corresponds to a load of 150 lb. per sq. in.
for a 5 -in. cube (Brown). At 14 ° F the modulus of rupture for 24 beams was
226 lb. per sq. in.
The experiments reveal only a slight influence of the orientation of the crystals upon the breaking strength in bending although after 20 days
beams, 54.5 inches long, allowed to bend under their own weight show a
deflection of 9t inches at the centre or 17% of the span, when the crystals
are vertical, and only 1 inch, or 2% of the span, when the crystals are
hori-zontal.
Bending strengths have been measured at still lower temperatures
for ice from the Arctic Ocean. The beams used measured 10 x 10 x 30 cm.,
the span used 20 crn , The load was applied as fast as possible either
per-pendicular to the surface of freezing (or parallel to the optic axis), or
per-pendicular to the axis (parallel to the base), or perper-pendicular to the sur-face nearest to the water (parallel to the optic axis).
Rupture in Bending Tests (Nazarov) (Ice from Arctic Ocean)
Temperature
°C of
Greatest Strength in kgm. per sq. em.
.L base 11 base ...l....water base
Depth in ice cover, crn , -30.8 -3 O. 8 -30.8 -38 -38 -38 - 1. 1 -13.4 -28 -36 30 39.0 35.0 52.0 29.0 20.0 24 23 40.0 37.5 50.0 55.0 30.0 33.5 40.0 20 20 25 15 30 5 8 18 28
IMPACT STRENGTH OF ICE
(a) Strength in Sudden Loading
When a mass moving at a velocity v hits one end of a light bar
firmly held in place, or when the bar falls, the length 1 of the bar is changed
until the total work done by the flying body against the tensions created in
the solid is equal to the kinetic energy of the bar. The deflection d pr oduc ed
in a bar of cross-section A is d = d st 2 v
+-
d g stwhere d
=
WI / AE is the elongation of the bar when the weight W is appliednot only
ｾｩ｜ｨｯｵｴ
any initial speed, but is, moreover, increased very graduallyfrom zero to its full value. It follows that even in the absence of initial speed
the sudden application of the full load produces twice the deflection obtained with a load increasing so slowly that there is always equilibrium between the
acting load and the resisting forces in the bar. Since the stresses set up in
the bar are proportional to the elongations, or contractions, produced by the
load, suddenly applied loads are more destructive than progressively increased loads.
In the work done with ice from the St. Lawrence river, the most
rapid rate at which progressive load could be applied to 5-inch cubes was 40
lb. per sq. in. in two seconds, but in a few other tests this load was applied
Crushing strength Ib/sq. in. Temperature 0 F 28 14 2 20 lb. per sq. per sec. 300
693
811in. 30 lb. per sq. in.
per sec. 343 500
The results are not conclusive.
(b) Shifting Loads
No measurements were carried out with loads shifted along a beam or an ice cover but practical experience is available on moving
loads sustained by ice covers on lakes and rivers. Old ice that has
been exposed to the sun and to air at temperatures not much colder than freezing becomes split into irregular pieces and has little sustaining
power. New ice, 1 3/5 to 2 inch thick, will bear the weight of a man;
when 3 3/5 to 4 in. thick, infantry marching in open formation; 4 in.
of ice, a man on horseback; when 10 to 12 in. thick, an army; 15 in.
ice supports railroad tracks and trains. Russian specifications are
a thickness of 20 ern, ice for a railroad car of 15 tons (Moskatov).
(c) Impact Strength
With moving loads falling on ice the stresses created in ice can
be increased at wilL Ifthe velocity is large in comparison with the
deflection that the weight would produce at rest, the tensile stresses in a bar of ice hit at one end by a weight W at a speed v is
s = 2E Wv
2
Al 2g =
Hence the stress produced by impact can be diminished not only by an increase in cross -sectional area as it would be under static conditions
but also by an increase in the length (or thickness) of the bar. A
similar formula is obtained for bending under the impact of a solid body. The stress is kept constant despite the increase in load when the thickness
in the direction of the impact is increased in the same proportion. Some
impact tests have been made with ice from the Arctic Ocean, shaped into
cubes 10 x lOx 30 ern, (Nazarov). The falling body striking the ice was
a pendulum bob with edges of about 5mm. radius. The length of the
Work for splitting ice in kgrn , rn ,
Tem.perature
IJ base
1
baseII
water baseof °C 29.5 - 1. 5 5.9 4.3 3.7 25 - 4 5. 1 4.6 21 - 6 6. 1 6. 1 5. 5 3 - 16 to - 17 5.9 5.7 5.8 (1 kgrn . rn , = 7.233 foot-pounds. )
The necessary work increases less m.arked1y than expected with a decrease in tem.perature, probably on account of increasing salt content
of the sam.ples. It is known that river ice splinters considerably when
EFFECT OF SALTS
The dependence of the properties of ice on the temperature is en-hanced by the presence of salts, because while water dissolves a large number of substances, at least up to a certain concentration, ice, being
a crystal, is unable to receive into its lattice any substance that does not
conform with its particular building plan according to the hexagonal
system. No substance is known to be isomorphous with ice. When,
there-fore, a sample of water containing salt is cooled until the freezing point
is reached, pure ice crystals only are formed while the salt, despite its
higher freezing point, remains in solution. The growth of the ice crystals
continues, provided that the temperature is reduced in proportion, and
the concentration of the solution increase s until a s tate is reached where salt and ice solidify at the same time as an intimate mixture of salt
crys-tals and water cryscrys-tals. The temperature at which this so-called eutectic
mixture is formed is the lowest temperature at which the solution can
ex-ist in the liquid form, and is the highest temperature at which salt
crys-tals and ice can exist indefinitely side by side.
The eutectic solution of potassium chloride and ice forms at -11. 1°C
and represents a concentration of 24. 6 gm. of potassium chloride in 100
grn. of water. With ordinary salt the eutectic mixture contains 26.3 gm.
salt in 100 grn, of solution, but the salt deposited is a hydrate, NaC 1. 2H 0.
The eutectic temperature is -21.2°C (-6.20F). 2
Composition of the Salt of Sea-Water
NaCl MgC1 2 MgS0 4 CaSO KCl
4
Rest grn ,per kgrn , (mills by weight) 26.9 3.2 2.2 1.4 0.6o.
1 34.4 grn, per kgm. of sea-water Chlorine 16.33 2.38 0.28 18.99The concentrations of salts in sea -water are such that the eutectic composition will never be reached in the open ocean even after a thick cover
of ice has been formed, and it is hence well nigh impossible by any cold
occurring in nature to solidify sea-water.
If freezing proceeds with great speed, then, of course, the salt contained in sea or river water has not necessarily time to escape into
the remammg liquid; it may become trapped between the ice crystals.
Unless it forms an uninterrupted jacket around the ice crystals, it is
gradually squeezed toward the boundary by the arrival of neighbouring
ice molecules attaching themselves to their likes. Similar effects are
obtained in melts of metals, but the mobility of the molecules is very much less than that of ice molecules because in every day use metals are far below their melting point.
Lowering of the Melting Point by Sea Salts
(gm. salt per kgm. sea-water, that is, mills by weight)
gm. gm. grn ,
per per per
kgm. t = °C kgrn . °C gm °C kgm. °C 1 -0.055 11 -0.587 21 -1. 129 31 -1. 683 2 -0.108 12 - O. 640 22 -1. 184 32 -1.740 3 -0.161 13 -0.694 23 -1. 239 33 -1.797 4 -0.214 14 - O. 748 24 -1. 294 34 -1. 853 5 -0.267 15 - O. 802 25 -1. 349 35 -1. 910 6 .0.320 16
-o.
856 26 -1. 405 36 -1.967 7 -0.373 17 -0.910 27 -1.460 37 -2.024 8 -0.427 18 - 0.965 28 -1. 516 38 -2.081 9 -0.480 19 -1. 019 29 -1.572 39 -2.138 10 -0.534 20 -1. 074 30 -1. 672 40 -2. 196 Note:Sea-water averages about 35 gm. of salts per kgrn , The average
temperature of the surface layers of the oceans is -1. 7°C at 800
N and S.
The first signs of freezing of ordinary sea-water are observed at 28.7°F
(-1. 8°C).
Detailed investigations have shown that ordinarily the ice from
sea-water contains some salt, about 4 or 5 parts per 1, 000 parts of ice
in place of the 35 parts of salt originally contained in sea-water. In newly
formed sea-ice the salt is uniformly distributed throughout the mass,
en-veloping the crystal grains as far as can be ascertained, but as the ice
ages, there is a migration of the salt from the interior to the surface,
and the salt content of the ice in the Arctic Ocean is taken as an indirect
measure of its age. It may decrease from 4 or 5 parts per thousand in
young ice to only 1 or 2 parts per 1, 000 in ice two months old, and the
ap-proach of s urnrn e r finds a great part of the original salt squeezed out and
appearing on the upper surfaces, where it is removed by wind and water.
pole, six to ten feet thick, is several years old and free from salts. "When ice forms in the fall, it is as salty as the water out of which it is made, and if you take a chunk of it and melt it you get brine unfit for
the ordinary uses of water. The ice remains salty all winter, but the
following spring, as soon as the warm weather comes, it begins to
freshen, and even though the cake be of considerable size it will freshen
enough for use in tea-making or other cooking by the end of summer. But the lagoon ice which has never been over six feet thick to begin with, thins down to a few inches by July and cakes of it are perfectly fresh by that time. " (Stefansson, My Life with the Eskimo p. 115).
Salts in water are responsible for the brittleness in artificial ice
and for the tendency of artificial ice to crack. Different sections of a country
have their own particular type of water, and the ice made from certain kinds
of water will crack sooner or later. That is, if a cake of apparently clear
and good ice is taken from the form in which it was frozen and left lying for five or ten minutes, it may be found to have cracked into several large pieces.
Cracking can be caused by stresses arising in a block of ice as a result of different expansion rates when different parts contain variable amounts of impurities.
A block of artificial ice taken fr orn a can in which it was frozen for
eight hours at -10°C to -15°C consists usually of three separate zones, namely, a strikingly clear crust around the top where the water froze slowly; it is
traversed by flat bubbles of air. This ice surrounds a conical plug of ice crumbs
with many air bubbles, the last portion to freeze. Below it is the main part
of the block frozen first in contact with the walls cooled by the brine; it
con-sists of plates perpendicular to the walls, the only impurities are air bubbles
that appear where the growing ice crystals meet in the interior of the block In this zone the impurities may amount to 0.02%, in the clear crust to 0.09%, and in the plug to 0.11% when the water supply contains 0.09% impurities.
With one per cent of rocksalt added to the water, the main part of the block shows the horizontal crystal plates rn o r e distinctly; weak ice
oc-cupies the entire centre of the block, beginning with slush at the top. The
concentration of the salt is 0.2% in the outer portion, 1. 7% in the core,
and 3. 3% in the liquid portion. This portion is not frozen after 24 hour s of
cooling. (G. 'I'arnrrian and K. L. Dreyer, Naturwiss. 22:613-614,1934). The aspect of the block is slightly different when salts are present
that are rrio r e soluble the lower the temperature. These impurities are
caught in the portions of the water which freeze first, the lower corners
of the can and the edges. They tend to fo rrn a white shell around the block.
Whatever the nature of the salt, when the block is allowed to warm
up, the less pure portions expand at a rate that is different from that of
trapped between the crystal plates has moreover, a lower melting point
and forms planes along which the ice is easily split. When ice
contain-ing salts is allowed to warm up from -20 ° C, it begins to contract at temperatures far below the melting point whereas pure ice expands until it has reached the melting point.
When ice forms at the surface of the sea, the temperature gradients
are more uniform than when an artificial block of ice is produced, and no
cracking occurs. On the contrary, salt-water ice when it warms up never
disintegrates into separate crystals as does fresh-water ice' it is tough
and reliable. Whilst fresh-water ice cracks like a window pane hit by a
stone, salt-water ice bends before breaking and gives warning that it is
not strong enough. According to V. Stefansson, in the fall an inch and a
half of salt-water ice is preferable to two inches and a half of fresh-water ice.
THE PRODUCTION OF LARGE SINGLE CRYSTALS
Blocks of artificial ice sometimes yield fragments which indicate by their behaviour in polarized light and in X- ray diffraction that they are
single crystals. These fragments are lO em. in length and 1 to 2 sq. em.
in cross-section. Such a piece is suitable as a seed for the production of
large crystals. It is given two opposite plane-parallel surfaces' one of the
faces is frozen to the outside of the bottom of a metal can containing a freez-ing mixture at about -10°C., and the opposite face is allowed to dip just below the surface of a pool of distilled water, boiled and cooled nearly to
zero 0° as rapidly as possible. The water is kept at that temperature by
a jacket of melting ice. Crystallization proceeds from the seed into the
water at the rate of a few mrn, per hour. Single crystals with dimensions of
the order of lO em. are readily produced.
If a clear and flawless single crystal of ice is exposed to the heat from the sun or an arc focused on a small region of its interior, a cavity
nearly filled with water forms. The ice-flower appearing in this cavity
indicates the orientation of the crystal axis (Adams and Lewis).
That an ice cover consists of separate large crystals is best seen when fresh-water ice thaws in the spring in places where it is not covered
by smoke and soot. In the spring freshets the northern rivers leave huge
blocks of ice stranded on the bottom lands. Stefansson reports how one
morning he passed one of these blocks deposited by the Coppermine River
and found it quite as high as himself. In the evening, when he returned
over the same ground, he was astonished to find the boulder of ice missing. A little search showed a flattened heap of crystals, some of them a foot or
more in length. "The whole cake had divided into separate crystals and
all of a sudden the forces of cohesion had given way and the whole thing had
these stranded bowlders of ice and give them a smart blow with a stick.
It happened now and then that one of them would crumble at a touch into
exactly such a heap. When entering upon the surface ice of the first of
the lakes between Darnley Bay and Langton Bay (13 June 1911), the ice was breaking up into needles or crystals in the manner of the ice boulders. A sharp pointed pole could be jabbed into the ice and forced between the crystals down to the water below, although the ice was at least three feet
thick (Stefansson, My Life with the Eskimo p. 322). Apparently the
crystal faces though invisible, reflect light and heat to and fro; they thus
favour the absorption of the radiation near the walls and the separation into prisrn s and needles.
To d ernons tr a te the crystalline structure of ice, Tyndall passed
a b e arn of light through it. Hexagonal cavities are produced in the ice,
the process of crystallization being as it were reversed. As the action
of the b e arn proceeds, each cell becomes filled with the water which it
occupied as ice. The centre of each unit is occupied by a bubble of water
vapour. The cells lie at right angles to the principal axes of the ice
crys-tals and parallel to the original freezing surface, the surface of easiest cleavage.
HEAT CONDUCTIVITY
The heat conductivity of ice is difficult to measure because when there is a flow of heat between a block of ice and a rn e tal plate frozen to it, there is always a discontinuity in the ternp er a tur e at the junction. It
is rno st ma r ked at the lowest temperatures. The rn o st recent
measure-rn ents give the following values.
Heat Conductivity
Milliwatt Calories B. t,u,
I
per in.t in °C per crn.v C per CIn. sq.ft. h.oF of
sec °C. 0 22.4 5.354 x 10_-3 15.5 106 32 3 x -10 23.2 5.545x10_ 3 16. 1 x 10 6 14 -20 24.3 5.808 x 10_ 3 -4 -30 25.5 6.095 x 10_ 3 -22 -40 26.6 6.357 x 10 -3 -40 -50 27.8 6.644 x 10_ 3 -58 -60 29. 1 6.955 x 10_ 3 -76 -70 30.5 7.290x10 -99 -6 6
(one rrriIl.iwatt per CIn. °C = 239 x 10 cal. em. sec DC. = 0.693 x 10 B. t , u ,
per in. sq. ft. h. ° F. )
The the erna.l diffusivity, k, per unit density and per unit specific heat
is 0.011 CIn. per sec. when the ternpe r a.tur e is between 0 and -30°C.
The the r mal conductivity of snow depends on the density pof snow
-3
heat conductivity 0.153 x 10 calorie per em. sec. °C., increasing with
the density according to the formula, k = 69.3 +69.3 (100 density) microcal
per em. sec. DC. The heat conductivity of snow is therefore from 30 to
3 times smaller than that of ice, the diffusivity
2.0
+
O.lp + 10.3p2D = sq em. per sec.
1000 is two to three times smaller.
It is known that Eskimo occupy their igloos only about 3 weeks, for
the heat inside melts the snow walls and as they cool off during the night, they turn gradually to ice and the house grows colder and colder.
The arctic snow from which igloos are built consists of tiny needles of ice, it is quite porous but nevertheless not a loose mass.
ULTIMATE STRENGTH OF ICE IN SHEARING
Tests were carried out on rectangular specimens of artificial ice
3 in. by 3 in. in cross-section. The average value of the shearing
strength in the direction parallel to the basal planes was 114 lb. per sq. in. and in the direction parallel to the crystal walls 98 lb. per sq. in.
The maximum value read was 353 lb. per sq. in. parallel to the walls of the crystal, at 30°F., and the minimum value 68 lbs. per sq. in. parallel to the basal plane at -12 ° F.
At temperatures below zero, greater values were obtained when
the load was applied rapidly. At temperatures above 200
F (- 6.70
C)
rapid application of the load was necessary to obtain reproducible results. The strength in shear of artificial ice is about 80% of that of
river ice (Finlayson).
Some older measurements reported from Russia (by Weinberg, 1936)
give 57 lb. per sq. in. for the shearing strength of ice. Whatever the
correct value, there is no doubt that where the necessary force is
con-venient to apply, ice is much more easily broken by shearing than by pressure.
The values obtained for the strength in shearing are comparable
with the figures deduced from punching. There seems to be a minimum
load below which punching does not occur; in one case a load of 5 kgm. (71. 15 lb. ) produced no observable effect in 24 hours, but when the load
was increased to 7 kgm. (99.6 lb), the deformation was rapid.
INTERNAL FRICTION (VISCOSITY) OF ICE
10 The values found for
tg.e
coefficient of viscosity of ice vary from10 grn , per crn , sec. to 10 grn, per crn , sec. for glacier ice whereas
the corresponding value for water is known quite accurately, O. 018 at 00 C.
and 0.015 at 5°C. It is claimed that where the flow of glaciers was most
accurately studied and measured (Hintereisferner, Pasterze in Austria)
the most reliable measurements gave value 1. 0 1014 gm. per sec. ern.
+
10% for the internal friction of ice.
EXPERIMENTAL WORK ON THE ADHESION OF ICE
It was observed at an early date that if ice is firmly frozen to
concrete it will break or crush before it can be detached from the
con-crete by p r e s s ure, shear in tension. An article by G. G. Bell gives
the following results on the strength of adhesion:
Temp. 0 F Size ice, Unit load at Unit adhesion
inch failure, lb to concrete, lb
30 2 x 3 370 195
30 2 x 2 504 228
32 3 x 3 395 158
32 3 x 3 250 116
30 3 x 3 420 185
The Adhesives Research Committee of the Department of Scientific and Industrial Research mentions in its Second Report (p. 41, 1922) experi-ments with lubricants and other substances between metal, glass and
fused silica surfaces. They showed that ice between fused silica surfaces
gives a very strong joint.
When a piece of metal is submerged in water and the water freezes, the ice adheres strongly to the metal surface, an effect which illustrates the molecular attrac tion between water and metal.
The force necessary to separate the ice from the metal surface may be taken as a measure of the strength of adhesion; referred to unit area, it will be designated by P, the extraction or breakaway tension, on the assumption that the forces of cohesion of the ice itself are sufficiently
large. If a weak plane S is present in the ice quite close and parallel to
the metal surface S the metal piece may become loose before the extrac-tion tension that corresponds to the forces of adhesion has been reached. The values of P may therefore scatter a great deal, depending upon the
perfection of the crystals. Other disturbing influences cause a reduction
in P, and the maximum values as well as the average values deserve consideration when the experiment is repeated.
Two kinds of stress can produce breakaway; either a force is applied that is parallel to the surface of separation of the metal and
ice, or a force that is perpendicular to the surface of separation. In
this latter case the measured value must be decreased by about 1 kgm. per sq. em. in order to take atmospheric pressure into account.
Three methods were used.
(1) Extraction of strips and wires, frozen into the ice. When S is
the total area to which ice adheres, and K the tangential force that
pulls the metal from the grip of the ice.
P
=
K/S(2) The wrenching free of cylindrical rods of r ad ius vr and immersed
length 1. At the upper end each rod is provided with a short lever arm
of Ieng th a , A wire attached to the end of the arm is loaded with weights
until the rod starts to turn in the ice. Then
Ka
P
=
r 1 S=
Ka 2 2n r 1The force relates to a shearing action as in the first method.
(3) Removal of plates frozen to the surface of ice, by means of a
perpendicular force K so that
P
=
K-lS
The force K was m.ea s ur ed by a dynamometer. The surfaces
were cleaned with care, first sandpapered, then washed with alcohol
and with distilled water. Caustic soda was also used at times. If
the surfaces were not clean, (e. g. when, for instance oxidized brass rods were used) the values obtained were lower by about 12%·
Results
For method (1) brass strips 1.5 em.• 0.85, or 0.65 em. wide
and 2..5 to 3.5 em. long were used. The temperature was about _120
C
(10.4°F). The measurements gave for
or
s
= 8.3 P=
4 (80 5.5 5.5 110 3.4 sq. em. 6.9 kgm. per sq. em. 180 lb. per sq. foot)The decrease in the value of P when the surface area S is made
larger is caused, apparently, by defect, at the surface of separation or in
the ice. When the values were extrapolated to S = 0, in order to eliminate
the influence of local defects, P = 12 kg. per sq. em. (about 240 lb. per
sq.f t,.}, Brass wires gave similar high values:
Diameter 0.9 m.m 0.4 mrn, S O. 87 sq. em. 0.39 sq. em. P 10.6 kgm. per sq. em. 12.6 kgrn , per sq. em.
Method (2) was used with brass rods 2 to 3 rnrn , in diameter and
2 to 3 em. length. The temperature was about -7 ° C. (19.4 ° F). Four
pieces of brass and four pieces of another metal were used in each test
in order to get a direct comparison between different metals. The
re-sults are shown in the table.
Average P Pmax Ratio Number of tests
Copper 17. 6 23.9 1. 25 7 Brass 6 14. 1 1 6 Zinc 25.0 34.5 1. 33 12 Brass 18. 8 29.8 1 11 Aluminum 24. 1 27.7 1.38 8 Brass 17.4 22.0 1 8 Iron 29.6 37.6 1.5 8 Brass 19.9 28.4 1 8
According to the ratio obtained for P (in kgm, per sq. em. the
ad-hesion of ice to metals increases in the order.
Brass Copper Zinc Aluminum Iron
1 1. 25 1. 33 1. 38 1.5
The values obtained for brass, by method (2) (Temperature _70 C),
exceed the values obtained by method (l){temperature - 12°C),; the reason must be sought in the brittleness of ice which becomes very pronounced below
- 10° C.
Method (3) proved to give consistent results provided that the pieces of metal be held in place during the formation of ice and that they do not
prevent the escape of air bubbles set free during freezing. The tests were
carried out as follows. In the vertical front wall of a zinc box some holes
were provided into which small discs of metal, the size of coins, were
placed and fastened with paraffin. Each disc was provided with a hook to
which the force was applied. After the extraction the discs were sometimes
quite smooth and dry; in some instances splinters of ice were seen to
ad-here to the surface. The temperature was -7°C (19.4°F).
Diameter Average P Pmax
2.2 em.
0.7 II
7.9 18
[kgrn, per sq. em. ) Here again the smaller areas give the higher values.
11.5 26
Tests with sulphur showed that near the melting point, 114°C, the
force of adhesion is practically zero and increases to a limit of 55 kgm.
solidification were often quite different from those measured 24 hours
later. (A. Sellerio).
More recent qualitative and quantitative determinations of the force required to remove ice from various surfaces are reported by the National
Advisory Council for Aeronautics. The surfaces were maintained at
temperatures below 32 ° F. by placing them in a box containing sufficient
solid carbon dioxide to hold the inside at the desired temperature. A
window was provided for visual observation.
Blocks 1 inch square were made of material for which the adhesion
to ice had to be measured. Two blocks were held in position 1/8 inch
apart by means of adhesive tape. The space between them was filled with
water, the water allowed to freeze, and the hook on one metal block
fastened to the bottom of the cold box. The shearing force required to
separate the blocks was measured by means of a hydraulic ram.
It was found that with ice adhering to a solid surface, the rupture
occurs in the ice at a loading of about 140 lb. per sq. in. lee will adhere
to any surface tried thus far with a force greater than the cohesive forces within the ice.
For Brass At 21°F Failure occurred at 130 Duralumin 25°F 132 Steel 21 of 139 lb. per sq. in. If the temperature of the ice was brought considerably below 0 ° F the ice tended to crumble.
Ice will not adhere to a surface when there is a distinct liquid layer
between the ice and the solid surface. If such a liquid interface is formed
the force required to remove the ice is little more than the resistance or pressure of the air tending to hold the ice to the surface, too low to be measured with the instruments used.
When ice was adhering to a greasy surface, failure occurred be-tween the ice and the grease at a loading equal to, or little greater than,
atmospher-ic pressure. For a viscous liquid the force measured was 15
lb. per sq. inch, for micarta with a greasy surface 53 lb. per sq. in. In all the tests the results scatter a great deaL (A. M. Rothrock and R. F. Selden)
A few recent tests by Roy W. Carlson at the Massachusetts In-stitute of Technology gave a figure of approximately 115 lb. per sq. in.
for the strength of the bond holding
t
inch plain steel rods in 4 in. cubesat temperatures between 4°F and gOF. Only two tests were made (Ice
and Refrigeration 100: 4, 1940)*
ICE FLOES AS LANDING FIELDS FOR AIRCRAFT
The polar cap-ice which throughout the year covers the deep central major portions of the north polar basin, is distinguished by great
solidity, the large size of its fields, and the thickness of its rafted hummocks
of ice blocks. It occupies 70 per cent of the polar basin, about 2,000,000 square miles; its margin follows roughly the I, 000 rn , depth of the ocean.
The movement of the cap ice is not completely known. There is
undoubtedly a movement from east to west from Point Barrow around
the Siberian continental shelf, and finally out into the Greenland Sea. The
wind is, no doubt, a major factor in keeping the polar ice in motion. Winds and currents may shove fields and floes in the polar sea one above the other to heights of 100 or 130 ft. and to depths of 330 to 700 ft.
Large areas of open water, known as polynyas, remain in the polar cap-ice, in particular a belt several hundred miles long north of the New Siberian Islands, and Peary's Big Lead north of Grant Land and Greenland.
Open places are encountered even in winter. On March 14, 1938, a wide
lead was observed between lat. 81 ° and 84°N. and longitude 122 ° to 127 °
150 miles long and varying from 20 to 500 yards in width (Sir H. Wilkins).
Ice that breaks away from the polar cap or from the fast ice along the shores invades the North Atlantic along the eastern coast of Greenland; another stream of ice, or pack ice, moves along the eastern side of
North America from the Arctic Island to the Grand Bank. Both streams are
augmented by icebergs broken away from the glaciers of Greenland, Spits-bergen, Nansen Land, Northern Land, and Bennett Island.
The remarkable sustaining power of large ice floes in quiet water
was pointed out and explained by H. Hertz as early as 1884. It remained
for the explorer R. Amundsen to take advantage of this property. When
the Schooner "Maud" was caught in the ice between the New Siberia Islands and Wrangel Island in June 1923, a Curtis single-engined plane equipped
with skiis was lowered on the ice. The first two flights from the ice floe
were successful. On starting for the third flight, the engine stalled and
the lower wing of the aircraft crashed into a pile of ice. During Amundsen's
1925 explorations between Spitsbergen and the North Pole, two Dornier-Wal flying boats took off from snow covered ice and landed on open water
(lat. 87°north, Longr lOvwe.s t}, Much valuable experience regarding flying
conditions in the Arctic was gained on this expedition and the possibility that aircraft could take off from ice floes was clearly demonstrated.
Soviet pilots followed with a series of similar attempts.
"The first place in this connection certainly belongs to the polar pilot M. S. Babushkin, killed all too early in a plane crash at
Moscow in 1937; he made a large number of landings and take-offs
on floating ice, in aircraft of different types, some of them provided
with floats, others with skiis. The first one of his flights was
carried out as early as 1926 during a search for the dwelling -places
of seals around the White Sea. It is necessary to note that at the
time no theoretical calculations existed and each pilot had to fear
and risk everything each tirne he was forced to land on an ice floe,
aviator would have done nothing but bring horne his plane in
safety, he had accomplished a heroic deed. This particular
skill reached its perfection in 1928 during the mercy flights (June and July) to the wreck of the dirigible Ita Ha, 20 or 30 miles north east of the most northeasterly Spitsbergen Islands.
Under difficult conditions, Babushkin landed on and took off from ice floes on no less than fifteen occasions, in a
sing1e-engine metal monoplane YU -13. Neither before nor afterwards
was such a number of landings in Arctic aviation made by a single pilot on landing places measuring approximately 200 x 550 sq. ft.
A large amount of experienc e on drifting floes of pack ice was gathered in April 1934 during the rescue of the stranded passengers of the steamer "CheLius k in!' which was crushed by jamming ice and sank on 13 February, in the
Chikehee Sea north of Kamtchaka. The "Cheliuskin" was
an ice-breaking freighter, constructed during 1933 in the
dockyards of Burmeister and Wesh, Denmark. The vessel
of steel, was 307 ft. long, 55 ft. wide, with a displacement
of 3,600 tons. In the last two hours during which the vessel
was afl oat, the passengers, numbering 104 (including 10
women and 2 children) were able to disembark upon the
sur-rounding ice floe, to unload tents, provisions, and building
materials intended for Wrangel Island. Within a week a hut
sheltering 50 people had been built; the others continued to
live in heated tents. An amphibian aeroplane Sh-2, which
had served for ice surveys during the expedition, was also unloaded.
All around the ice floe were numerous channels of open water; the heaped-up ice blocks reached heights of 60 feet but three miles from the encampment there was an area of smooth ice suitable for the landing of aeroplanes and the Sh-2 was removed to this place, because the ice on the flow began to show cracks.
Rescue expeditions were organized on all sides. The pilots Kukanov, Kopnin, and Liapidevsky in U elen and at Cape Severny were instructed to fly at the first
sign of favourable weather. Three aeroplanes were
avail-able, the T-Z at Cape Severny, and the ANT-4 and a light
aeroplane U -2 in Uelen. On 4 Ma r ch, Liapidevsky landed
at the ice aerodrome, took on board the women and children,
and brought them safely to Ue Ien, He left fuel for the Sh-2
in the camp so that the pilot, M. S. Babushkin, would be able to fly it in an emergency.
G. A. Ushakov, Vice-Director of the Chief Adrrrirri s tr ation of the Northern Sea Route, and the pilots Levanevsky and Stepnev, were sent to Arne r ic a to undertake flights fr orn Alaska. They
bought two passenger planes fr orn the Pacific -Alaska Airways
Corporation, and took off fr orn NOITle. Levarievskyts plane was
forced down by icing near Cape Onrnan and was wrecked in the landing, but on 3 April the second Arn.e r ic an aeroplane, piloted by Stepnev
arrived at Uelen. On 7 April the weather p er rni.tted to fly to the
caITlp and to take five rn e n to the shore. On the s arrie day one of
seven aeroplanes R-5, which had been brought by the stearn e r
"Srriol en s k " fr orn Vladivostok to Oliutorsk arrived at Uelen. Fair visibility allowed the pilots, Karnarrin and Molokov to fly to the
caITlp on April 10 followed by Stepnevt s plane. Four landings
were rna da on the ice, and 22 people r erriov ed , On that day the
caITlp itself was experiencing the strongest pressure, a high ice rampart fell upon the c arnp, crashed the hut and pushed it into
the water; the aerodrome was entirely broken. On the
follow-ing day seven landfollow-ings were carried out and 22 rn en were taken off by Molokov and Karnariin, assisted by Doronin and Vodiapanov
who had arrived with another of the R-5 planes. Only six rneri
r erria.ined on the ice, arnorig theITl the wireless operator Kr enk e l and the captain of the vessel; they were rescued on 13 April,
after a stay of two months on the ice floe. A dozen landings had
been rna.d e on the ice floes without an accident.
The experience gained in this rescue operation,
COITl-bined with the experience of the polar pilots A. D. Alexeyev, M. 1. Koslov and others enabled the Soviet Union to undertake an ex-pedition to the North Pole, to land on the polar ice with four four-engined aeroplanes (with Vodiopianov and Babushkin in the N-170, Molokov in the N-17l, Alexeyev in N-l72 and Mazurnk in N-169),
to establish the polar research station on a drifting ice floe, and
as a lasting conquest of the North Pole, to unveil the secret of the rnov ern errt and the behaviour of the ice floes in the heart of the
Arctic. II (Moskatov)
The four-engined Soviet aeroplanes that landed on skis near the Pole had each brought 21- tons of various supplies for the party of four that was to carry out scientific observations for nine rn on th s on the ice. All the planes landed safely on skis after their 500 -rrril e trip fr om
Rudolph Island to the North Pole. The landing field was an ice floe 10 ft.
thick, 21- rn.il.e s long by
Ii
rrril e wide; in May it was quite level and stable but after a m onth a wide fissure was discovered under one of the tents.By 1 July, pools of water had formed everywhere under the snow.
To-wards the end of July ice walls and pressure ridges had begun to appear
on the floe, one of the ice walls was 30 feet high and nearly 330 feet long.
The water on the floe became so deep that it would have been possible to
sail a ship across the floe. At the beginning of October the floe had
drifted to latitude 85 0
, but the increasingly cold weather and the
At the end of the year the floe measured 98 x 164 sq. ft. On 19 February, 1938, the four members of the party were removed from the floe by ice breakers, just after an aeroplane from the rescue ship had landed on the
landing field Ii miles from the encampment. The dwindling ice floe had
drifted 1560 miles from a point within 35 miles of the North Pole towards
the coast of Greenland, at 710
lat. N.
Outstanding ac hievements during 1940 were a flight from Tixie
Bay (Lonely Island) to the "Pole of Inaccessibility" (lat. 840
N, long.1600 W ) ,
and a flight from Dickson Island to a point lat. 82 "N, long. 83oE.
The most recent landings on the pack occurred in March and April
1941 on a flight from Wrangel Island. Ivan Cherevichni and four others
flew from Moscow and made a descent on the pack in lat. 81°2f N., long.
180°E. The next flight was to lat. 78"N, , long. 1760 40! E., and the third
landing was atlat. 78°N., long. l700E. The ocean depths were found to be
between 6, 000 and 12, 000 ft.
PROPER TIES OF SEA ICE
(Translated from the article: Contribution to the study of the
properties of sea ice, by V. S. Nazarov. Transactions of the
Arctic Institute 110: 101-108, 1938).
In 1935, the Polar Ice Laboratory was organized on Lonely Island
(Kara Sea). In its first year it studied the impact strength of sea ice and
the strength in repeated bending.
The results were as follows: 1. The strength of ice depends on its
structure and on the arrangement of the crystals. The structure of ice
depends on the conditions during its formation and the composition of the
water from which it is obtained. 2. The ice that forms on the sea early
in winter, or in the middle of winter, when the temperature is just suf-ficiently low, is weaker than the ice of the cover that grows slowly
dur-ing the winter. For reasons to be indicated, the change in strength is
about 10 per cent or 12 per cent. 3. This condition is due to the fact
that the first ice crystals floating in the water congeal to a mass with ir-regular orientation of the crystals, but that in the second ins tanc e, when
ice grows from an existing ice cover, the crystals form an orderly
arrangement and produce a strong mass of ice. Sea ice forrned in stormy
weather, or in strong currents under the snow cover, must, for the same
reason, be weaker than the ice formed in calm weather and in calm water.
4. The strength of the ice depends on its temperature, it increases with
decreasing temperature. 5. An increase in the salt concentration
re-duces the strength of ice at one and the same temperature. 6. Fresh
water ice has greater impact strength than sea ice, but the tests on fresh water ice are rendered difficult by the large quantity of splinters. 7. Tests
show that between -2°C and - 8 ° C (28
i
oF to 17io F.) the force requiredfor breaking an ice cover by applying it to the plane surface in contact with
