Soil shrinkage characteristic curve in clay soils: Measurement and prediction

Laboratory determination of soil hydraulic characteristics (HC) is performe d on cylindrical confined soil cores, while resin-coated small natural aggr egates are prevalent for determining the Soil Shrinkage Characteristic Curv e (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 objecti ves of this study were (i) to investigate differences between the SSCC obta ined on resin-coated natural aggregates (volume V = 20-30 cm(3)) and on cyl indrical confined cores having a volume (650 cm(3)) close to that of cores used for HC laboratory determination, (ii) to test the performance of diffe rent models proposed for analytical interpretation of the SSCC, and (iii) t o derive regression equations predicting the SSCC from routinely measured s oil physical properties. Using twenty-one Sicilian soils of variable shrink -swell behavior, we found significantly larger specific volume (n), indicat ing less shrinkage, in the cylindrical confined cores. The investigation al so 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. The se results suggest that incorporation of shrinkage in HC of clay soils shou ld be based on the SSCC measured or predicted on cores with geometry and di mensions as those used for routine laboratory measurement of HC.