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

Abstract The present work has the purpose of presenting the geotechnical and mechanical characterization of the fine sandy lateritic soil (SAFL), as well as its performance in the field as sub-ballast layer in railway pavement. The activity in the field is the application of this material in the project of expansion of the rail yard in the municipality of Acailândia - MA. Despite the fact that SAFLs are properly established in road pavements in Brazil, especially in the more than ten thousand kilometers of the state of Sao Paulo, their use in railway pavement requires special attention, particularly due to the dynamics of rainwater. Because of it this material is named “Alternative” on this paper. The material studied was characterized and subjected to repeated load tests for the determination of the resilient modules (RM) and evaluation of the permanent deformation. The California Support Index test, traditionally known as CBR, was also performed. In the “in situ” evaluation of the mechanical properties, the Dynamic Cone Penetrometer (DCP) or South African penetrometer was used as an alternative to define the natural terrain support capacity, thus allowing a comparative study between the field conditions and the laboratory. The present research is part of a larger project in which it is proposed to review the criteria of project of the permanent way, adapting them to the tropical conditions of climate and soil formation. The laboratory tests results, indicated satisfactory values for resilient module, low permanent deformation for state of stresses compatible with the 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 setting of ballast aggregates in the sub-ballast, even after almost three years of operation.