Soil shrinkage characteristic curve in clay soils: Measurement and prediction

Laboratory determination of soil hydraulic characteristics (HC) is performed on cylindrical confined soil cores, while resin-coated small natural aggregates are prevalent for determining the Soil Shrinkage Characteristic Curve (SSCC). Because of the different geometry and volume of clods and cores, incorporation of shrinkage in HC of clay soils could be affected by the use of SSCC determined on natural aggregates or on confined cores. The objectives of this study were (i) to investigate differences between the SSCC obtained on resin-coated natural aggregates (volume V = 20-30 cm(3)) and on cylindrical confined cores having a volume (650 cm(3)) close to that of cores used for HC laboratory determination, (ii) to test the performance of different models proposed for analytical interpretation of the SSCC, and (iii) to derive regression equations predicting the SSCC from routinely measured soil physical properties. Using twenty-one Sicilian soils of variable shrink-swell behavior, we found significantly larger specific volume (n), indicating less shrinkage, in the cylindrical confined cores. The investigation also proved the good fitting of a two-line model to the measured SSCC and the possibility to predict the basic shrinkage line from the clay content. These results suggest that incorporation of shrinkage in HC of clay soils should be based on the SSCC measured or predicted on cores with geometry and dimensions as those used for routine laboratory measurement of HC.