Use of Chilled Mirror /Dew-Point Method (WP4C) to Develop Soil Water Characteristic Curve for Coastal Silty Sand with a Comparison of the Existing Analytical Models

Soil Water Characteristic Curve (SWCC) is one of the methods to study the behaviour of unsaturated soil. This study presents the SWCC for Sri Lankan coastal silty sand developed using chilled mirror dew-point technique WP4C and compares the performance of a few prediction models. SWCC was also developed experimentally using pressure plate and suction-moisture sensors, to verify the results obtained using WP4C. The fitted SWCC curve was developed using Van Genuchten's (VG) model. The prediction models of Arya and Paris (1981), Aubertin et al. (2003), and Wang et al. (2017) were used to compare the performance using their own suggested values and the more suitable values for this study as the model parameters which were estimated using the least square method. This study shows that chilled mirror dew-point technique which is incorporated in WP4C instrument can be used as a fast and reliable experimental method to develop the SWCC for sandy soils compared to other experimental methods. The Wang et al. (2017) model is better suited for estimating the SWCC through analytical methods for this soil type, using either the recommended values in this study or proposed values by the authors for the modal parameters.