Predictive Model for Soil Shrinkage Characteristic Curve of High Plastic Soils

Soil shrinkage characteristic curve (SSCC) is the relationship between gravimetric water content (w) and void ratio for a soil drying under zero external stress. It is mandatory for determining the soil-water characteristic curve and modeling water transport in high plastic soils, which exhibit significant volume change. The knowledge of SSCC is required for calculating the degree of saturation or volumetric water content from the known w. However, the measurement of SSCC is extremely tedious and time consuming, particularly for highly plastic clays like bentonite. Therefore, this study attempts to develop a predictive model for SSCC of highly plastic soils based on easily measurable index property, plasticity index (PI). Four bentonites and nine bentonite–fly ash mixes were used to encompass soils with a wide range of PI. The results were used to study the influence of plasticity characteristics on SSCC. The key parameters of SSCC; minimum void ratio, water content at air entry (wAE) and the shrinkage limit (wS) was effectively correlated with PI. The measured SSCCs were quantified using the Fredlund, Wilson, and Fredlund (2002) model, and equations were proposed to estimate the model parameters using PI. The efficacy of the proposed model was demonstrated using an independent data set of bentonite and its mixes with fly ash as well as data from the literature. It was found that the proposed model can predict the SSCC of highly plastic soils with reasonable accuracy.