The performance of unsaturated shear strength models of silt soils using the soil water characteristics curve

Abstract

Various studies have investigated soils' unsaturated shear strength properties using the modified triaxial testing machine, which is costly, and time-intensive for standard geotechnical procedures. Examining the unsaturated shear strength due to variations in climatic conditions in tropical regions is crucial to prevent overdesign and ensure cost-effectiveness. The experimental determination of the unsaturated shear strength of silt soil and the evaluation of the prediction performance of unsaturated shear strength models using the SWCC is key to this study. This study assessed the SWCC and unsaturated shear strength of silt soil samples collected from five locations in Bahir Dar City, Ethiopia. Additionally, the obtained SWCC and the saturated shear strength parameters are used to predict the unsaturated shear strength properties of the soil. The pressure plate test was conducted to establish the SWCC by applying matric suction values ranging from 33 kPa to 1500 kPa. A curve-fitting technique was utilised to provide comprehensive data over the suction range up to 106 kPa using MATLAB-R2021a. The experimentally determined unsaturated shear strength data, obtained through modified triaxial tests, were compared with the predicted unsaturated shear strength data from the empirical models. The comparison shows that the empirical models developed by Fredlund et al. (1996) and Khalili and Khabbaz (1998) yield reasonable estimates. However, an increase in percentage errors was noted, indicating that the empirical models deliver inadequate results for Bahir Dar silt soil and are unsuitable for accurately predicting unsaturated shear strength functions using the remaining unsaturated shear strength models.

Keywords

• SWCC
• Matric suction
• Pressure plate