Understanding fine soil deformation in pavements: a master curve-based investigation for Amazon soils

The performance of soils and granular materials must be considered in relation to the main deterioration mechanisms in pavement structure design. This study aims to evaluate the use of fine-grained soils as unbound materials in pavement applications. For this purpose, physical, chemical, and mechanical characterization tests were conducted. Repeated load triaxial tests were performed following current Brazilian standards and considering different soil saturation conditions. Five widely used mathematical models were employed to assess the resilient modulus under different moisture conditions, with the Compound and Universal models showing the best correlations. As moisture content increased, a reduction in resilient modulus was observed at higher stress levels. Regarding permanent deformation, the master curve approach was applied to obtain the parameters adopted as inputs for simulations within the mechanistic-empirical pavement design software, FlexPaveBR version 2.1.5. The model results adequately represented the plastic behavior of the analyzed conditions. The simulation results indicated differences between considering bonded and unbonded granular layers. The results also indicated that the use of fine-grained soils without stabilization can be considered for subbase layers, provided that triaxial testing is conducted and the materials demonstrate satisfactory performance under mechanistic-empirical evaluation.