Contribution to the use of alternative material in heavy haul railway sub-ballast layer

Abstract

The main objective of this work is to characterize geotechnical and mechanically a fine sandy lateritic soil (SAFL), as well as to evaluate its performance as sub-ballast layer in railway pavement. For this, the Resilient Modulus (RM) and the evaluation of the permanent deformation of the studied material were realized, in addition to the California Support Index test, traditionally known as CBR. This material will be used in a project of a railway yard in the municipality of Açailândia in the state of Maranhão. Thus, in the “in situ” evaluation of the mechanical properties, the Dynamic Cone Penetrometer (DCP) was used as an alternative to define the natural terrain load-bearing capacity, thus allowing a comparative study between laboratory and field conditions. This research is part of a larger project in which it is intended to review the criteria of permanent way design, adapting them to the tropical climate and soil formation conditions. However, when it comes to lateritic tropical soils, these materials have a natural cementation due to the high concentrations of Fe and Al oxide-hydroxides, which provides these materials with a peculiar structural behavior. The laboratory tests results indicated satisfactory values for RM, low permanent deformation for stress states compatible with field and shakedown type behavior, even for higher stresses. The results of field tests with DCP equipment and visual analysis indicated a very low penetration rate, absence of pumping of fines and no intrusion of ballast aggregates in the sub-ballast, even after almost three years of operation.