Avaliação da função de calibração usada para estimativa da umidade volumétrica de diferentes solos com a técnica de TDR

Abstract

Purpose: This dissertation evaluates the use of a probe that uses the technique of time domain reflectometry, known as TDR, to estimate the volumetric water content (θ) of different soils. The TDR advantages include the possibility of determining θ through the use of a non-destructive technique that allows performing severals measurements at the same place over time. However, the results obtained depend on the calibration, meaning the relationship between the apparent relative dielectric constant of the soil and its water content adopted. Thus, this research verifies, through field and laboratory tests, the validity of using the calibration of the TDR, known as "Universal Equation", proposed by Topp et al. (1980) for different soil types and volumetric water content. The tested soils are the barriers group from the city of Serra, located in Vitória, ES, and present more than 30% of fines. Glass microspheres were also tested, used as standard soil. It is also evaluated if some of the existing equation in the literature can be used for calibration of the materials studied. Results: The experimental results show that the calibration proposed by Topp et al., (1980) do not apply for the tested soils for θ between 15% and 30%. However, as for the glass microspheres, the measures were within the range. Only the equation proposed by Medeiros et al. (2011) showed good results for the tested soils. Conclusion: We recommend a specific calibration for each studied soil.