The publication under review was presented in summary form to a joint meeting of the American Society of Civil Engineers and the Engineering Institute of Canada held in Toronto in July 1950, with a view to subsequent publication by the American Society of Civil Engineers. The many problems of ice pressure in connection with both static and flowing water raise questions of physics as well as mechanics and, as Mr. R. F. Legget, of the National Research Council of Canada, has pointed out in this Journal,Footnote * are not unrelated to glacial problems. It is possible, therefore, that glaciologists may be of assistance in their solution.
The Symposium is introduced by a clear and concise report from the sub-committee, which sets out the present ascertained state of knowledge, design practice and research trends in five countries. A valuable bibliography is given of eighteen publications on the subject, which is followed by three original contributions. The report stresses that, despite general appeals for information, the response was disappointing, probably indicating the dearth of factual data on the subject.
Of the five countries mentioned in the report (Switzerland, Norway, Sweden, Canada, U.S.A.) only the last three appear to have carried out serious research work. Indigenous ice problems are not sufficiently serious in the British Isles and Western Europe generally to stimulate intensive research—but one would have expected some information to have been forthcoming from the French and Italian Alps zone. Russia is not mentioned and presumably present international relations do not make it easy for research information (if such exists) to be made available.
Dr. Bertil Löfquist, the State Power Board, Sweden, describes his own laboratory (freezing chamber) experiments for the Swedish Power Board. He draws attention to certain experimental difficulties which affect proper correlation between analytical, experimental and field investigations. Among these are the formation of tension cracks in the ice during temperature drop with edge restraint and the subsequent refreezing of water in the cracks before further temperature rise occurs, which affect the accuracy of experimental results. The experiments suggest that maximum thrust might occur in ice sheets of half a metre thickness at somewhere about −4° C. temperature.Footnote †
Mr. A. D. Hogg, Hydro-Electric Power Commission, Ontario, gives a straightforward and well-illustrated description of practical field investigations being carried out by the Hydro-Electric Power Commission of Ontario at Des Joachims and Pine Portage dams. The “equipment” comprises a completely free panel of the upstream face of the dam, about 10 ft. square, which is suspended so as to be capable of freely responding to ice expansion. Behind the free panel will be situated load compensation (i.e. deflection cancelling) cells which apparently keep the panel hard against the ice and record the force necessary to maintain a rigidity equal to that of the rest of the concrete dam face. Details of these cells are said to be still in the design stage.
Mr. G. E. Monfore, Bureau of Reclamation, U.S.A., describes field investigations carried out at Eleven Mile Canon Reservoir for the U.S. Bureau of Reclamation in an effort to correlate analytical and experimental results. The scope of the work includes the development and perfection of pressure-recording gauges and measurement of solar radiation and absorption. An interesting result obtained was that strong wind gusts caused rapid variation in recorded pressures.
It is interesting to note from the report that the apparent practice in Switzerland is to draw down the reservoirs in early winter to ensure that ice (if not broken up) can only exert thrust at predetermined and non-critical levels. This seemingly simple expedient, while not helpful in advancing the study of ice thrusts, might suggest a further field of investigation, namely, means of preventing or reducing the effects of ice thrust, rather than providing for large thrusts at the upper critical levels. One wonders whether there might also be scope for the development of elastic or flexible panels, similar to the flexible fenders provided to reduce impact from berthing ships. It is noted that in Norway apparently considerable reductions in thrust have been assumed where dams have sloping upstream faces.
The interesting results which have so far been obtained will doubtless be even more valuable when the present investigations have proceeded further.
