Results of Measurements of the Specific Weight and Fracture Strength of Ice on the Tom River before the 1912 Ice Breakup
Abstract Generated abstract
This report presents measurements of the specific gravity and fracture strength of ice from the Tom River near Tomsk in March 1912, shortly before the onset of ice drift. Ice samples taken repeatedly from the same location were examined with improved laboratory apparatus for density determination and with a fracture testing device, with results tabulated by layer and date. The observations showed relatively consistent specific gravity values but substantial variation in breaking strength, especially as the ice became more heterogeneous and submerged near breakup. Comparison with the previous year suggests that fracture strength may be a more sensitive indicator of approaching ice drift than specific gravity, although the author emphasizes that more numerous and repeated annual measurements are needed to support this conclusion.
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Results of Measurements of the Specific Gravity and Breaking Strength of Ice on the Tom River Before the 1912 Ice Drift
B. P. Weinberg.
This year ice began to be delivered to the physics laboratory for investigation starting on March 18, every three days (28.3, 21.3, and 24.3). The first days of Easter week caused an interruption: the fourth piece was delivered on the evening of 30.3, and even then with great difficulty, since the ice was already under water; later it was altogether impossible to obtain ice. On April 5 the ice on the Tom began to move.
The ice was delivered from one and the same place—opposite the Gorokhov landing stage, about thirty sazhen from the left bank. The first piece had been broken out on the eve of the day on which it was delivered; the others—on the very same day. The upper layers of the ice, to a depth of 5–7 cm from the surface, were milky in color; lower down there occurred only small interlayers of the same low transparency; in general, however, the ice was clear, with a small number of air bubbles. In the last piece, however, there were considerably more such bubbles, and some of them—narrow and long—pierced the cut-out pieces through their entire thickness (perpendicular to the freezing surface). The thickness of all the pieces was about 75 cm.
The apparatus was essentially the same as last year; but, for the convenience of determining the specific gravity of the mixture of linseed oil and turpentine, we used an areometer (from 0.86 to 0.92 with divisions of 0.001), and, for greater constancy of temperature, placed this mixture in the pail AA (Fig. 1), provided with a lateral branch C with a lamp glass D inserted into it, and set on a stand inside another pail BB. The space between the walls
Fig. 1.
of the pails ...
bucket was filled with snow, and all measurements were carried out not in the open air, but in the laboratory. The hydrometer was placed in branch \(D\).
The apparatus for testing resistance to fracture remained the same as before; but, so that the strips to which the side bearing platforms were attached would not rise upward during the test, two slots were made in the upper board of the apparatus, and the strips themselves were provided with screws and nuts, which also secured them at the required distance from one another.
The results of the measurements, carried out chiefly by V. D. Dudetsky and V. D. Kuznetsov, may be expressed by the following two tables:
Table I. Specific gravity of ice.
| Piece. | No. 1. 18.3.12 |
No. 1. 19.3.12 |
No. 2. 21.3.12 |
No. 2. 22.3.12 |
No. 3. 24.3.12 |
No. 4. 31.3.12 |
|---|---|---|---|---|---|---|
| I—upper | 0.9117 | 0.9112 | 0.9006 | 0.9111 | 0.9036 | |
| II— | 0.9179 | 0.9147 | 0.9068 | 0.9137 | 0.9150 | 0.9127 |
| III—middle | 0.9157 | 0.9148 | 0.9134 | 0.9145 | 0.9154 | |
| IV— | 0.9157 | 0.9141 | 0.9142 | 0.9148 | 0.9149 | |
| V—lower | 0.9156 | 0.9137 | 0.9145 | 0.9147 | 0.9146 |
In the measurements of 18.3.12 the vessel with the side branch for the hydrometer was not yet ready, and the hydrometer readings were taken from above; a correction has been introduced into the corresponding results on the basis of a subsequent comparison of readings from above and through the liquid, but nevertheless these results are not fully comparable with the others.
Table II. Resistance to fracture.
| Piece. | No. 1. 18.3.12 |
No. 1. 19.3.12 |
No. 2. 21.3.12 |
No. 2. 22.3.12 |
No. 3. 24.3.12 |
No. 4. 31.3.12 |
|---|---|---|---|---|---|---|
| Upper | 17.6 16.4 |
16.4 17.1 |
9.1 4.0 |
9.7 17.3 |
7.5 6.1 |
|
| Middle | 11.6 11.7 |
12.0 | 9.5 | |||
| Lower | (24.6) (29.6) |
15.8 13.7 |
11.5 14.6 15.7 |
19.0 20.7 |
10.4 15.3 |
The values in parentheses were obtained, probably, when the fracture occurred in a plane parallel, and not perpendicular, to the freezing surface, since on the first day attention was not always paid to this circumstance.
If the results of this year’s observations are compared with the results of last year, what is striking is the greater constancy of the values of specific gravity, readily explained by the improved method of determining it, and the more considerable fluctuations in resistance to fracture. In general, the resistance of the present ice was greater than that of last year, which may be partly connected with the fact that the observations began a longer interval of time before the ice drift. The last piece, however, proved less strong than last year’s, and this—in connection with the greater inhomogeneity of the ice—gave me grounds to state, in the general conclusions from these experiments, communicated by me on the day following the beginning of the ice drift to the Mayor of Tomsk: “if one also takes into account the circumstance that, after March 30, the ice remained under water for another week, then—other conditions being equal—the ice of the present year will be less dangerous in ice jams than the ice of last year.”
The ice drift this year passed much more quietly than last year; the jams were eliminated more quickly, the height of the rise was smaller, but answers to the questions whether this should be attributed to the very early ice drift and the unfriendly onset of spring, or to the small thickness of the ice, its considerable inhomogeneity, and its lesser strength by the beginning of the ice drift, can be given only after similar observations have been repeated from year to year. From the experience of these two years one gets the impression that changes in resistance to fracture are a more sensitive indication of the imminence of the ice drift than changes in specific gravity; but, since in measurements of strength the individual differences of separate specimens from one and the same piece of ice have a much greater effect, it is necessary to carry out a considerably larger number of tests than we carried out last year and this year.
Tomsk, 17. 4. 12.