Harvard Tests Reveal Secrets of ice Pressure

Manawatu Times, Volume 61, Issue 64, 17 March 1936, Page 10

Harvard Tests Reveal Secrets of ice Pressure

Discovery of tremendous ico pressures, far greater than engineers have hitherto taken into account, may lead to large savings in improved frostresistant highways, according to .investigations carried on at the Harvard Graduate School of Engineering, by Professor Arthur Casagrande and announced recently.

Exhaustive tests disclosed that forces excited by these ice pressures beneath highways causing Leaving and cracking, far exceeded aii theoretical expectations.

Professor Casagrande’s installation last year of one of the most complete ‘‘cold room” laboratories for soil research in the world, made these studies possible. With such, equipment he can reproduce and control natural ice formations at will.

Perhaps the most important discovery made, was that pressure exerted by crystalising ice against soil in which it is confined, is not the same for ail freezing temperatures as was generally supposed. It was found that the pressure increases in proportion to the amount of temperature decrease below the freezing point. Thus, at low temperatures such as are reached in the more northerly regions of Canada, exceptionally huge pressures are built up beneath highways. Furthermore, it the freezing progresses slowly enough, ice layers may continue to grow indefinitely. Professer Casagrande also discovered that in sandy and silty soils, water for such "growing" ico layers is supplied from free ground water in the soil beneath.

Investigations carried on in New Hampshire in co-operation with the United States Bureau Public Roads and the State Highway Department, in which heavings as high as ■ six inches were found, led to the building of Harvard's new cold room. .. Under extreme conditions, such heaving may react more than a foot, said Professor Casagrande. "In clean sand and gravel we have found no growth of ice layers, either in field or laboratory observations. Such materials are therefore advised for use extensively in highway construction in places where tho underlying soil would cause serious trouble if it wero penetrated by frost of any considerable depth.” Apparently, in certain soils, the water between soil particles not only freezes but such ice crystals as are formed continue to grow, forming layer after layer which utimatcly reach considerable thicknesses.'

‘‘They tell me that was a wealthy girl you were flirting with at Bournemouth?" ‘‘-Yes, her father made a fortune in some kind of mine." "No; another fellow camo along.”