Uncertainty in the estimation of hysteresis of soil–water characteristic curve

The soil–water characteristic curve (SWCC) contains key information on unsaturated soil properties and is reported to be hysteretic (i.e. the amount of water at a given suction during the wetting process is less than that during the drying process). In this paper, an equation for quantifying the hysteresis of SWCC due to the ‘ink bottle’ effect is derived. The derived equation shows the uncertainty in the estimated wetting SWCC. In this paper, an equation for quantifying the hysteresis of SWCC due to the ‘ink-bottle’ effect is derived. The derived equation shows the uncertainty in the estimated wetting SWCC. In addition, an equation for estimating the hysteresis of SWCC due to the entrapped air is also proposed. The uncertainty of the entrapped air volume for the compacted mixture of sand and kaolin is analysed using the statistical method. The uncertainty of the entrapped air volume is incorporated into the proposed equation for estimation of the wetting SWCC. Consequently, the equations for estimation of the wetting SWCC due to the ink bottle effect and the entrapped air are proposed and the uncertainty of the estimated wetting SWCC is also presented. The proposed equation is then verified using experimental data measured in this study and published data from literature. The uncertainty in the estimated wetting SWCC (or the hysteresis of SWCC) agrees with the data obtained from the experiments conducted in this study.