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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Article
Optimization of the Mix-Design System for the Sub-ballast Railroad
Author(s)
Martínez Soto Fernando1 and Di Mino Gaetano1, 2
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DOI:10.17265/2328-2142/2017.05.002
Affiliation(s)
1. Department of Civil, Environmental and Materials Engineering (DICAM), University of Palermo, 90128 Palermo, Italy;
2. Department of Civil, Environmental, Aerospace, Materials Engineering (DICAM), University of Palermo, 90128 Palermo, Italy
ABSTRACT
Bituminous sub-ballast is an alternative solution to the unbound
granular sub-ballast used in the railway track due to several benefits that it
can provide. Indeed, it contributes to maintain the moisture content in the
subgrade unchanged during all year. This decreases the subgrade deterioration
process. Moreover, the presence of bituminous sub-ballast can also reduce
vertical stiffness variations on the track; it can have a positive effect in
the maintenance needs at transition sections (bridge-embankment) and in the
attenuation of the vibrations induced by the rail traffic. Despite the
importance of the presence of the bituminous sub-ballast to conceive the
construction and/or rehabilitation of sustainable infrastructure, in literature, there are only fragmentary
information regarding the definition of benchmark criteria for their mix
design. The superpave mix design approach used in road domain is applied
systematically in the railway domain, without being adjusted for different load configuration of
the rail track system. This research work aims at defining the benchmark
criteria for the bituminous sub-ballast mix design to reduce the approximations
involved in the recipe optimization due to the limitation of applying the superpave
system in the railway domain. The methodology proposed aims at selecting the RESAL (rail equivalent single axle load) and
therefore, transforming the
entire traffic spectrum on the track lines in number of ESALs. Afterwards, the Ndesign has been calculated
as function of the rail traffic level. Finally, a case study of bituminous
sub-ballast mix design has been investigated for a first verification of the
methodology proposed.
KEYWORDS
Sub-ballast, superpave, railway, bituminous layer, ESAL, Ndesign.
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