Abstract Brazil has an extremely limited railroad network compared to other developed and developing countries. There are projects to expand this mesh. Knowing that the cost of implementing a railroad is high, research for solutions that allow cost reduction is of great importance. But the parameters of the materials used in the subgrade and sub-ballast layers are from other countries, which can cause the cost to increase to meet these parameters. Through strength parameters and mineralogical analysis, it is possible to use or not fine tropical soils as a layer of railway pavement. A critical analysis of the standards that are used to scale and/or verify whether a particular soil can be used in these layers was undertaken. For this, the following tests were performed: Granulometry, Atterberg Limits, Compaction, California Support Index (CBR or ISC), Expansion, MCT Classification Test (Miniature, Compacted, Tropical), Dynamic Triaxial and X-Ray Diffraction. From the results, it could be seen that although one of the soils is thin, it presented satisfactory results in relation to the use in layers of the railway pavement. It was verified that it is necessary to use more modern tests, focusing on mechanistic dimensioning for dimensioning pavement layers.

Abstract The granulometric range used has a direct influence on the life of the ballast layer when subjected to the load generated by rail traffic. However, in Brazil, we have only two size ranges to be used. The publications related to the subject matter under study express the need for a continuous grain size strip, different from the ones usually used in our railways. This more continuous band would provide less deformation and a reduction of degradation, granting a longer ballast life. To verify the influence of granulometry, a Dynamic Ballast Test Equipment was used to simulate railway traffic. The results show that if we use a more uniform granulometry, a direct influence on the deformation and the breakage index is evidenced, and consequently, a shorter useful life. The study highlights the need to study continuous granulometric bands for the rail ballast.