Abstract
Subgrade moisture variation monitoring and control is important due to its influence on road pavement performance and service life. The precise application of non-invasive techniques such as time domain reflectometry (TDR) and ground penetration radar (GPR) in compacted tropical soils depend on calibration models, that consider their mineralogical composition and geotechnical properties. The present work aims to determine calibration models that relate dielectric permittivity with moisture variation in compacted tropical soils. TDR technique was used with low-cost probes and soil calibration columns developed at laboratory for reading dielectric permittivity and define its relationship with moisture. Results showed that through laboratory standardized procedures, it is possible to determine calibration models according to the required accuracy in moisture control in the subgrade. It was found that the high density and magnetic properties of tropical soils significantly influenced the determination of dielectric permittivity and consequently in moisture estimates, hence reaffirming the need of specific calibrations for these types of soils .
Highlights
Moisture is considered an important variable in road pavement and subgrade performance
This study aims to determine calibration models which allow relating dielectric permittivity with moisture content variation in compacted tropical soils
According to the results analysed in this study, the implemented laboratory procedures were shown to be effective in establishing through calibration models, the relationship between dielectric permittivity and moisture variation in compacted tropical soils
Summary
Moisture is considered an important variable in road pavement and subgrade performance. Pavement rapid deterioration under traffic conditions is directly related to variations and excessive moisture accumulation in the subgrade and in pavement constituent layers (Bastos, 2013). Time Domain Reflectometry (TDR) and Ground Penetrating Radar (GPR) are non-destructive methods commonly used for real time measurement and monitoring the soil moisture content and in pavement and subgrade. These electromagnetic methods are useful when samples and the site under observation need to be preserved and generally employed in monitoring situations over time, aiming to assess and visualize moisture seasonal variations. Examples of studies employing both techniques to estimate and monitor moisture in civil engineering materials and structures are shown below: (Klemunes, 1998), (Jiang and Tayabji, 1999), (Al-Qadi et al, 2004), (Ekblad and Isacsson, 2007), (Benedetto, 2010), (Khakiev et al, 2014), (Thring et al, 2014), (Benedetto et al, 2015), (Tosti and Slob, 2015), (Fernandes et al, 2017) and (Bhuyan et al, 2018).
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