New discoveries relating to frost action in soils, which may lead to large savings in improved frost-resistant highway construction, have been made at the Graduate School of Engineering by Arthur Casagrande, assistant professor of Civil Engineering.

The tests showed that tremendous ice pressures, much greater than commonly supposed by engineers, may form in winter beneath highways, causing them to heave and crack.

Cold Room Lab

The investigations of frost action were made possible by Professor Casagrande's installation last year at the School of Engineering of one of the most complete "cold room" laboratories for soil research in the world: In this laboratory natural ice action in soils can be imitated and controlled at will.

One of the important discoveries made by Professor Casagrande is that the pressure exerted by crystallizing ice against the soil in which it is confined is not constant for all freezing temperatures, as it was generally supposed, but increases in proportion to the amount the temperature falls below the freezing point.

Thus at low temperatures, as in northern states during the winter months, tremendous ice pressures, much greater than would have been anticipated under older soil theory, may form beneath the highways. Further, if freezing is sufficiently slow, ice layers may continue to grow indefinitely, the tests showed conclusively.

Professor Casagrande also discovered that in sandy and silty soils, water for the growing ice layers is supplied from free ground water in the soil beneath. The faster the freezing ice is carried out, the smaller is the amount of water supplied from beneath, he found.