THE BEHAVIUOR OF SUB-SOILS FROM THE PO RIVER EMBANKMENTS: AN EXAMPLE OF TRANSITIONAL BEHAVIOUR IN NATURAL SOILS

A series of triaxial and oedometer tests has been analysed on highly heterogeneous alluvial sediments from the flood plain of the River Po in Italy. It is shown that the framework applicable to behaviour of the soils may be correlated with the grading and that as the fines content reduces the mechanics change from a clay type of behaviour that follows the key assumptions of Critical State Soil Mechanics to a transitional mode in which many of these assumptions break down. This transitional behaviour has only previously been seen for a variety of reconstituted soils, including some taken from the same site, and even if the data are imperfect, they provide the first evidence of transitional behaviour in soils with their natural geological fabric.