Some clayey soils of Northern Italy have been analysed with the aim to develop a simple methodology that could be used to predict and classify the swelling/shrinking potential in the study area. This paper presents the preliminary results obtained. More than 200 samples have been submitted to geotechnical and chemical-mineralogical tests. Published methods based on a number of index properties were used for the evaluation of the swelling/shrinkage potential. The reliability of these different methods for the studied soils was checked by comparing their results and through the direct measurements of the maximum swelling pressure developed by the soils. All the geotechnical data were statistically analysed to determine if any single property or a group of properties could be used for prediction and classification of swelling/shrinkage potential of the studied soils. Among all the variables, the methylene blue value presented a better significant correlation with the maximal swelling pressure. A new classification of swelling/shrinking potential based on methylene blue value has been proposed.
Swelling/shrinking soils are the cause of many problems in roads, the building of shallow foundations, slope stability and underground works. The annual damage is regarded as being of natural disaster proportions (Alexander, 1993; Steinberg, 1998). Therefore the identification and delineation of hazardous zones of swelling/shrinking soils is necessary for hazard mitigation planning and management. There is a high number of factors that influence the swelling/shrinkage phenomenon (lithology, mineralogy, slope, climatic index, land use, etc...) and which are used for the construction of swelling/shrinkage hazard maps (Oteo et al., 1995; Meisina et al., 1998). Among these the geotechnical soil characteristics are of great importance. They permit the evaluation of swelling and shrinkage potential in a better manner. However, their determination often requires sophisticated and expensive equipment which may not be available for practical purposes.