Análise mecanística-empírica de um pavimento dimensionado pelo método do DNER : estudo de caso da duplicação da rodovia RSC-287 em Santa Cruz do Sul.

Abstract

The current method for pavement design used in Brazil, known as “Método do DNER”, has as main input parameters the CBR value (California Bearing Ratio) e “número N”. By using such parameters the pavement structure is overprotected against shear failure but the fatigue of the asphalt layer is not taken into account, given that this is the most common pathology found in Brazilian highways these days. Furthermore, it is not considered the determination of tensions, deformations and deflections on the structure that can lead to the appearance of cracks. Due to this problem, mecanistical concepts were created that, through software analysis, utilize Elasticity Theory to determine the response of the pavement to the load applied to them, causing it to show pathologies. Being that said, the work to be presented has as its main objective to design a pavement structure through the “Método do DNER” followed by its analysis by machanistic-empirical concepts so that improvements can be made in the structure designed by the Brazilian method so the pavement can resist to fatigue cracking. In order to make it possible, soil samples were collected from the RSC-287’s duplication construction site, in Santa Cruz do Sul/RS, and taken to laboratory to undergo characterization tests as well as Proctor compaction and CBR tests so that it could be possible to design the pavement using the “Método of DNER”. Afterwards, the soil samples underwent the triaxial shear test in order to determine their resilient moduli, parameter to be used as input to analyze the pavement structure using a software. In addition, a traffic study was conducted using data from the toll gates located in the city of Venâncio Aires/RS. The AEMC tool, part of the SisPav program developed at UFRJ (Federal University of Rio de Janeiro), was used to determine tensions on the top of the subgrade, deformation on the top of the asphalt layer and the specific deformation at the bottom end of the asphalt layer when subjected to a single axle load. It was noticed that, as the thickness of the surface course increases, deformation on the top of the surface layer and the tension on the top of the subgrade tend to be lower. In addition, a fatigue life of approximately two years was found when the asphalt layer (or surface course) thickness is of 10 centimeters, being that an age far lower than the ten years life spam used to design the structure with the Brazilian method. By altering the thickness of the outer layer (asphalt layer), it was found that in order to have a structure the will last for a period of time close to 10 years, under the current traffic load estimated, the thickness of the asphalt layer should be of 20 centimeters.