Um catálogo simplificado de estruturas padrão em pavimentos flexíveis dimensionadas pelo Método Medina aplicável à RMF

Abstract

In Brazil, road transport is responsible for transporting more than 65% of cargo and 95% of passengers. It is also noteworthy that most Brazilian highways are built with flexible pavement, around 99.0% (CNT, 2022). Aware of the significant importance of this modal and with the purpose of supporting the development of the sector, the Pavement Sizing Catalogs seek to expand the possibilities in the choice of structures for road projects and facilitate the access of the technical staff to the new techniques developed, as well as the own pavement dimensioning method. Although CBR is the stiffness parameter used in the conventional empirical design method (Souza, 1981) of pavement structures, Medina (DNIT, 2018) is the new method of national design of pavements, of mechanisticempirical design, uses as main parameters of stiffness the modulus of resilience and the permanent deformation of the materials. In view of this, the main objective of this research is to develop a catalog of standard structures of flexible pavements, dimensioned through the Medina and, based on the geotechnical behavior of local soils and on the active traffic in the Metropolitan Region of Fortaleza (RMF). For this purpose, both a sampling effort was conceived, in which soils and gravel were collected in the RMF, as well as an experimental program for the physical and mechanical characterization (MR and DP) of the collected materials. In order to recognize the natural subgrade and materials available for RMF road works, soils located in natural deposits and slopes within the limits of the study area were extracted. Finally, catalog sheets were produced from various tests and simulations carried out in the MeDiNa software. As for the AASHTO classification, the behavior of the studied soils, for the most part, was classified in class A-2-4, a result that validates the model by RIBEIRO et. al (2013) with a hit rate of around 57%, although the hit rate reaches up to 71%, regarding their probable behavior as granular layers in pavements. As for the CBR, the analyzed soils showed an adaptation rate of 0.56 in relation to the model by RIBEIRO et. al (2013). The collected soils were submitted to the triaxial test and presented average modules in the range of 380 to 550Mpa, however, a low direct correlation was found with the predictive model by Ribeiro (2016). But, by adjusting the model according to the predicted MR ranges, it was possible to obtain MR values closer to the real ones, with a variation of more or less 100 MPa. According to the procedures, analyzes and evaluations developed, this study demonstrated the efficiency of the simplified European laboratory methodology, for obtaining and understanding the occurrence of DP in granular materials from the FMR, reducing the execution time of the tests and resources. The tested soils showed low deformations, as well as the mixtures stabilized with soil and gravel. For the simulation of pavement structures, depending on the subgrade and traffic, the subgrade was classified according to the AASTHO classes and the traffic according to the classification of Bastos (2016). It was found, during the simulations, that in general the stabilized mixtures did not add to the performance of the pavement. For some sub-regions of the RMF, it was not possible to obtain structures with the materials studied for extremely high traffic, which was circumvented by proposing the use of ash and lime according to Vasconcelos (2018). As a final result, a simplified catalog of standard structures was generated, for flexible pavements, designed by Medina for the Metropolitan Region of Fortaleza - CE, suggesting itself as a quick and preliminary reference guide for local road projects.