The measurement of the Soil-Water Characteristic Curve (SWCC) is an important initial step in applications that require knowledge of the partially saturated soil behavior. The relationship between the pore-water suction and the soil water content is known as the SWCC. This relationship is fundamental to the description of the behavior of unsaturated soils. SWCCs are hysteretic, with the drying limb plotting above the wetting limb. Hysteresis is generally occurring due to entrapped air inside the pores. In this study, only the drying limb of the SWCC was measured. The standard method in determining the SWCC relies on the pressure plate (PP) apparatus (D3152-72, 1994). The PP apparatus is generally used to determine the equilibrium water content for various pore-water suctions allowing the construction of SWCC. The PP methodology is time consuming, expensive and elaborate. Thermocouple psychrometer (TCP) provides an alternative device to the PP for the SWCC measurement. TCPs are a simple and reliablemethod in the measurement of the soil total suction in the field and in the laboratory (Tsai and Petry, 1995). Previous studies (Daniel et al., 1981, Meerdink et al., 1996, Chiu and Shackelford, 1998, Yaldo, 1999, and Merayyan and Miller 2000) showed that the use of TCPs in the measurement of total suction in order to construct the SWCC of compacted finegrained soils is acceptable. In the current investigation, an evaporation scheme that utilizes TCPs was used in the determination of SWCC. This schemeis referred to as the "Evaporation Technique." This study will attempt to use the Evaporation Technique in the SWCC determination. In order to construct the SWCC using the Evaporation Technique, samples were prepared using three soil types (Plasticity index (PI) 7-60) compacted at or near wet of optimum water content. The findings of this investigation are in good agreement with the data reported in the literature using the PP. Samples were arranged in the order of their PI. Higher PI samples at the same suction resulted in less water content. The Evaporation Technique created as part of this study is proven to be efficient, and reliable.
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