New device and method for soil shrinkage curve measurement and characterization

There is a need for a conceptual and analytical model to describe and interpret the common shrinkage curves of structured soil samples. In this work, we propose a new device for direct shrinkage measurement of unconfined structured soil samples and discuss the relevance of parametric models of the shrinkage curve to fit the experimental data. The experimental procedure consists 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 identified. The points of transition between the different shrinkage zones of the shrinkage curve are considered as characteristics of the shrinkage process. They are used as parameters to model the experimental shrinkage curves by linear shrinkage zones separated by curvilinear transition ones. The efficiency of two parametric models to fit the experimental data and to provide the characteristic points of the curve are compared and discussed. A new procedure for fitting the shrinkage curves of structured soil samples and for determining the best position of the characteristic points on the curves is proposed.