SNCF engineering is conducting laboratory and field tests to find out whether
road base asphalt can be
used in the roadbed of
railway tracks. The idea,
proposed by highway
builder Colas, is to use this
asphalt to replace the
gravel of the subballast
layer. According to Colas,
the thickness of this layer
could be reduced from
20 to 15 cm and the
subbase from 50 to
35 cm on soil of average
bearing capacity. On
a stronger subgrade,
the subbase could even
be eliminated.
The savings in materials
and transport costs
would be significant in
regions where fill is
unavailable locally. Using
asphalt would also
change construction
methods. Until recently,
railway equipment could
be installed only with
railway vehicles, i.e. after
the rails had been laid.
Road equipment is being
used more frequently
now, but it can damage
the subgrade. A layer of
asphalt would provide a
paved roadway before
the first ballast was
spread on it that road
equipment could use for
installation work, with no
risk of damaging the
subgrade.
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