Calibration of a reflectometer for water flow studies in un-saturated soils.

Abstract

This work aims to the calibration of an equipment based on TDR technique for water flow studies in unsaturated soils, based on indirect measurement of the humidity, matricial suction (ψ) and unsaturated hydraulically conductivity k(ψ), in an not deformed soil profile. This be possible by recurrent laboratory tests of the traditional and unsaturated soil mechanics, from not deformed samples retired to different depths during the construction of a well, where the probe rods of the TDR be installed. From the tests, polynomial equations had been gotten to relate the behavior of the variation of the period of time of the electromagnetic pulse covered by probe rods TDR with the variation of the humidity of the soil and Van Genuchten models (1980) to relate the humidity with (ψ) and k(ψ). The results had shown that, for the calibration of the humidity in this type of soils, a four-degree polynomial adjusted appears like the best alternative in relation to the existing expressions in places where these theories had been derived. Additionally, it was observed, that the biggest variations of (ψ) and k(ψ) will occur between the saturation and 10% of humidity due to peculiarity of the retention curve. Finally, the present calibration is presented as an useful and practical expedient for hydrodynamic studies of unsaturated soils. Keywords: calibration, reflectometer, content of water, unsaturated soil.