Influence of Saline Pore Fluid on Soil Behavior during Evaporation

Abstract

Saline conditions govern soil behavior during evaporation, thereby affecting the water budget in semi-arid regions. This research examined the effects of saline pore fluid on soil behavior during evaporation. The results indicated volumetric reductions of about 5% for silty sand and about 15% for lean clay. The evaporative flux for silty sand decreased from 26 mg/m2∙s to 22 mg/m2∙s in StageII, remained at a constant flux in StageIII, and decreased to 13 mg/m2∙s in StageIV. The air entry and residual suction values were found to be 5 kPa and 100 kPa, respectively, and the total suction of about 5000 kPa merged with matric suction near the Stage II/Stage III boundary. The swell–shrink curve (SSC) was J-shaped with the only void ratio decrease in Stage II. In contrast, the evaporative flux for lean clay decreased from 30 mg/m2∙s to 15 mg/m2∙s in StageII, to 10 mg/m2∙s in StageIII, and then to 5 mg/m2∙s in StageIV. The air entry and residual suction values were 5 kPa and 2000 kPa, respectively, and the total suction during Stage II and Stage III ranged from 1000 kPa to 6000 kPa, with an average value of 3500 kPa. The SSC showed a major void ratio decrease in Stage II, marginal decrease in Stage III, and no decrease in Stage IV. Under high demand, the evaporative flux for silty sand was constant at 180 mg/m2∙s in StageIII and decreased to 50 mg/m2∙s in Stage IV, whereas it decreased for the lean clay from 230 mg/m2∙s to 145 mg/m2∙s in StageII, to 95 mg/m2∙s in StageIII, and then to 25 mg/m2∙s in StageIV. For both soils, the total water loss was found to be six times higher than that under low demand.