Gullà Giovanni (a); Mandaglio, Maria Clorinda (b); Moraci Nicola (b), 2005, Influence of degradation cycles on the mechanical characteristics of natural clays., 16th International Conference on Soil Mechanics and Geotechnical Engineering, September 12-16, 2005, Osaka, Japan, pp. 2521–2524, Osaka - Japan, 2005,
URL: http://www.cnr.it/prodotto/i/88712

On low depths, soils are exposed seasonally to frequent wetting-drying and freezing-thawing cycles; the degradation effects of these cycles are more pronounced in clayey soils. The number of cycles is due to periods of rainfall and variations in air temperature. Such processes can trigger shallow instability essentially controlled by the physical weathering of soils. An experimental study was carried out to investigate how the physical weathering, reproduced by laboratory wetting-drying and freezing-thawing cycles, affects the mechanical behaviour of natural clays in the superficial layers. For this purpose block samples of Pliocene clays were taken from a slope in Southern Calabria (Italy). They are overconsolidated stiff clays which can be classified as to high plasticity clays (CH). Different specimens were trimmed from the block samples and they were subjected to different numbers of wetting-drying-freezing-thawing cycles and then tested in oedometer and direct shear tests. Results of oedometer and direct shear tests seem to show that the physical weathering has caused a degradation of the bonding due to an insufficient ability to resist this cyclic process. The variations of peak shear strength are pronounced in the first month then they may be regarded as essentially constant. The wetting-drying-freezing-thawing cycles also cause a decrease in compression index and an increase of swelling index.

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