Calibration of an empirical model for moisture content assessment and monitoring in compacted tropical soils used in the subgrade of road pavements

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.