Effects of infiltration and evaporation on geosynthetic capillary barrier performance

Abstract

This study includes an experimental investigation of the transient movement of water in unsaturated soil layers underlain by a geocomposite drainage layer (GDL) during cycles of infiltration and evaporation. The distribution in volumetric water content with depth in a soil column having a height of 1350 mm underlain by a GDL was measured during transient infiltration. The capillary break effect was observed to affect the soil up to a height of 500 mm above the GDL, with an increase in volumetric water content up to 20% above that expected for the case of infiltration under a unit hydraulic gradient. Due to the long duration of this test (2000 h), a shorter 150 mm high soil column was also evaluated to investigate the soil–GDL hydraulic interaction during cycles of infiltration and evaporation. The capillary break was observed to have re-established itself after infiltration was stopped and the soil near the interface dried. The suction and volumetric water content measured in the soil at breakthrough were consistent after multiple cycles of wetting and drying. The conditions in the soil after each breakthrough event corresponded to the point on the drying-path water retention curve of the nonwoven geotextile where it transitioned from residual to saturated conditions.