New device and method for soil shrinkage curve measurement and characterization

There is a need for a conceptual and analytical model to describe and inter pret the common shrinkage curves of structured soil samples. In this work, we propose a new device for direct shrinkage measurement of unconfined stru ctured soil samples and discuss the relevance of parametric models of the s hrinkage curve to fit the experimental data. The experimental procedure con sists of simultaneous and continuous measurements of the diameter, height, and weight of an initially saturated soil sample as it dries. The shrinkage measurement can be completed for the full moisture range in a short time ( 2-3 d), and all shrinkage phases can be established easily and accurately i dentified. The points of transition between the different shrinkage zones o f the shrinkage curve are considered as characteristics of the shrinkage pr ocess. They are used as parameters to model the experimental shrinkage curv es by linear shrinkage zones separated by curvilinear transition ones. The efficiency of two parametric models to fit the experimental data and to pro vide the characteristic points of the curve are compared and discussed. A n ew procedure for fitting the shrinkage curves of structured soil samples an d for determining the best position of the characteristic points on the cur ves is proposed.