Engineering Properties of Unsaturated Cohesive Soil subjected to Freezing and Thawing

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Road pavement and gutter have been damaged due to frost heaving of the subgrade and the subbase in winter and decreasing of shearing resistance of soils of the subbase in spring.Considering those phenomena, this study aimes to make appear the actual damade conditon in field and engineering properties of soils subjected to freezing and thawing in laboratory.The results of those studies are as follows ;1.Field Resarches(1) Many frost heaving disasters occcured in Akita, Iwate and Fukushima prefectures in 1984-1986. Especially, in 1986, number of damages were 752, 1648 and 1958 in each prefectures. Also frost heaving disasters have occured every yeares at the cold region in Nagano, Yamanashi and Gunma prefectures.(2) Those frost heaving disasters were caused at the high grround water region in Hokkaido and even at the low ground water area on the cold region in Nagano, Yamanashi and Gunma prefectures if the subbase has the high water content.2.Laboratory Tests(1) In the open system tests, frost heaving occured easily in the silty soils. However, it was scarcely caused in sandy soils because those soils had high permeability.(2) In the closed system, volume changes of the unsaturated soil during freezing process resulted in expansion and shrinkage phenomenen according to the degree of the saturation of soil and during melting process shrinkage phenomena were always caused.(3) It was cleared that the shearing strength of the unsaturated soil subjected to freezing and thawing was decreased due to decreasing of the suction force between soil particles.