Estimation of Soil Moisture Characteristic Curve Based on Soil Particle Size Distribution Curve and Local Void Ratio for the Studied Soils in the Marvdasht Region, Province of Fars

The relationship between soil moisture and soil suction is called soil moisture characteristic curve، and its measurement is time-consuming and expensive. One of the estimation methods of soil moisture characteristic curve is using the soil particle size distribution curve and bulk density، which contains a scaling parameter (). In this study، 9 soil samples with silty clay and silty clay loam textures were selected from the Marvdasht Region in the Province of Fars، and soil moisture characteristic curve of each soil was determined. Then، the soil particle size distribution curve of each soil was estimated based on the Fooladmand and Sepaskhah model (FS) and the Fooladmand and Mansuri model (FM). Also، the local void ratio was considered for different segments of soil particle size distribution curve. The linear procedure with local void ratio (LN) and Logistic procedure with local void ratio were used for determining the scaling parameter. Therefore، the soil moisture characteristic curve of each soil was estimated with four different methods، and all of them were compared with the determined soil moisture characteristic curve. The results showed that using the FM model for estimating the soil particle size distribution curve to estimate the soil moisture characteristic curve was better than that of the FS model. In general، the results indicated that the procedure of FM-LN was appropriate for estimating the soil moisture characteristic curve of the studied soils in this study.