The Soil Water Characteristic Curve for Non-cohesive Soils


  • Idris A. Abd, Haidar Mekkiyah, Mohammed Y. Fattah


The soil water characteristic curve (SWCC) is very important because it has information about the soil performance. In this paper, three types of the silty sand soil were taken from Kirkuk city north of Iraq: natural soil, overconsolidated soil, and natural soil mixed with 10% pure clay soil. Eleven samples were prepared from each type of soil. After drying the soil samples in the oven, distillated water was added to the soil sample in order to get a specific degree of saturation for each sample; 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100% and for every type of soil. After that, the matric suction was measured by using Irrometer Watermark to draw the soil water characteristic curve SWCC. The results showed that the air entry value (AEV) for the natural soil, natural soil mixed with 10% of pure clay, and overconsolidated soil is 17 kPa, 25 kPa, and 27 kPa, respectively, also the residual degree of saturation for the natural, mixed and overconsolidated soils is 18%, 20%, and 23%, respectively. The SWCC variables change with changing the soil type.

Keywords- AEV, SWCC, Unsaturated soils, and Matric suction.