Evaporation in soils: Electrical conductance and optical observation

摘要

The evaporation in soils naturally occurs and its characteristics have significant implications on geotechnical issues in unsaturated soils and relevant geostructures, fluid flows in hydrology, and agricultures. In particular, the existence of wetting front and the unsaturated zone plays an important role in slope stability in soils. This study examines the evolution of evaporation zone using optical observation in conjunction with the measurement of electrical resistance. The saturated sands in a transparent chamber that is placed on the balance are subjected to drying. The front view of drying phenomena is captured and the electrical resistance is obtained along the height using two electrodes system with time. Results show that the wetting front identified in the images does not necessarily coincide with the low value of electrical conductance, highlighting the presence of unsaturated regions and significance of long range connectivity of water phase that determine the conductance values.