Using compression curve characteristics to estimate water content by the van Genuchten model

van Genuchten model is a well-known and most widely used model for the estimation of soil water retention curve. The parameters of this model have been estimated by different estimators such as soil texture. But so far the properties of compaction curve have not been used to estimate the parameters of van Genuchten model. Compaction curve is one of the soil mechanical properties and shows the relationship between the stress-strain with the elasticity modulus. Soil water retention and compaction curves have similarities. Measurement of soil water retention curve is time-consuming and costly while the measurement of compaction curve is cheap and needs less time. For this study, 150 soil samples (distributed and undistributed) were collected from five provinces of Iran. Soil water retention was measured at 12 suctions and the compaction curve was obtained using uniaxial apparatus in the confined sample. In this research, 6 levels of estimators including compaction characteristics and equations coefficients were used to estimate water content. In general, results showed that the use of compaction curve was useful to estimate the soil water retention curve. The second and sixth levels with the estimators of Pc-Cc-Cs and parameters of stress-strain model (indirectly), respectively along with basic soil properties had higher estimation accuracy compared to other estimator levels. The reason for the excellence of these estimators can be due to their correlation with van Genuchten model parameters and mechanical concept of estimators. Moreover, the similarity between the two curves was one of the reasons for the appropriate estimation of soil water retention curve.