A laboratory-testing program was undertaken to investigate the effects of different soil fabrics and testing methods on the soil water characteristic curve (SWCC) using a poorly-graded sand (SP). Four different reconstitution energies were used to generate different soil fabrics within a narrow band of possible densities, as limited by the mechanical properties of the soil particles. Water retention tests were performed using the transient retention imbibition's method (TRIM) and Fredlund device to develop a statistically representative laboratory SWCC over the range of densities and soil fabrics. A specimen preparation method was used to prepare specimens in a highly repeatable manner to reduce laboratory uncertainty by controlling the three principal components of specimen reconstitution, i.e., mass, water, and applied energy. The change in soil fabric, obtained through variance of the compactive energy, has a significant impact on shear strength and physical soil properties in low confinement zones where unsaturated behavior is prominent. However, the same fabric variance does not produce a statistically significant change in the SWCC compared to the change in testing method used. Therefore, a representative mean SWCC is presented for use in predictive behavioral algorithms for soils under ultralow confinement.
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