Hadush Seged (PhD)Nuru Ismail2024-04-252024-04-252013-09https://etd.aau.edu.et/handle/123456789/2875Many researchers have done researches on unsaturated soil mechanics worldwide to bring the unsaturated soil mechanics in to practices. Among those researches some of them focused on simplifying the complex and expensive testing mechanism by developing models which can be used to predict the unsaturated soil parameters from basic soil prosperities such as Grain Size Distribution (GSD) and Plasticity Index (PI) along with the saturated shear strength parameters. Soil water characteristic curve (SWCC) was proved to have good relationship with the unsaturated soil parameters. In this study an attempt was made to check whether those developed models would work for expansive and red clay soils found in Addis Ababa. Using the model developed by Fredlund and Xing (1994) along with the correlation equation given by Perera et.al (2005), family of SWCC for soils found in Addis Ababa has been plotted. It was observed that the family of SWCC plotted was out of the widely referenced family of curves developed by Zapata et.al (2000) to some extent. Even though the family of curves seems to be out of the range provided by Zapata et.al (2000), the model gave good prediction for the unsaturated shear strength parameter Φb. The percentage error between the measured values of unsaturated shear strength parameter Φb in previous researches of Habtom (2010) and Getaneh (2010) with predicted unsaturated shear strength parameter Φb in this study was compared. For red clay samples the percentage error lie in the range 2.07 to 6.37% for suction ranges of 36.67 to 52.9 kPa and at lower suctions of 16.75 and 21.5 kPa the percentage error ranges from 11.42 to 25.39% . For expansive soil samples for suction of 23.1 and 32.9 kPa, the percentage error is in the range from 3.86 to 6.13%. For suction values of 14.5 and 52 kPa the range of error is about 9.45 to 13.40% and for suctions of 38.8 and 48.6 kPa the error lies between 18.94 and 38.84%.en-USSoil Water CharacteristicGSDPIExpansive SoilsRed ClayThesis