Capillary rise in sedimentary silts using scale model and high suction heads

Abstract

Capillary rise studies in fine soils are necessary to better understand its hydraulic properties. Two sedimentary silts yellow (A) and gray (B) were subjected to capillary rise with suction head of 2 m. Additionally, the yellow soil was also subjected to capillary rise in a reduced model using an acrylic box. For testing tubes, the results showed that the capillary water was able to saturate the column of both soils up to 70 cm in height, where the air entry point was found. The water took 41 days to reach 200 cm in soil A and 65 days in soil B, while approximately 1.6 kg of water entered both soils due to the suction head. The measured permeability coefficient (kc) varies from 0.0001 cm/s (soil A) and 0.00008 cm/s (soil B) at the height of the air entry to 0.00002 cm/s at 2 m height. The matric suction registered values greater than 500 kPa in the unsaturated phase of the soils. As for the reduced model for yellow soil, compacted in 3 different densities, the results showed that the velocity of water rising through the capillaries of soil increased when the soil was compacted with a higher dry unit weight. Over time, the coefficient of permeability decreased in all cases from 0.0005 cm/s to 0.0003 cm/s. The matric suction in the soil registered values of 600-800 kPa for saturation degrees between 90%-100%. It was verified that the rise height vs. time curve is mainly influenced by the molding porosity, saturated state permeability coefficient and air entry height.