Problems with Railway Track Drainage in Finland

Several studies have shown that water plays a significant role in phenomena that
weaken track geometry. For instance, water may cause frost heave, thaw softening,
attrition of ballast, and weakening of the load-bearing capacity of a track.
Functioning drainage can prevent water damage, but no researched data on the
magnitude of the impacts exist.
Most of the Finnish rail network has been built in times when earthworks were
kept to a minimum. Drainage generally functions well along new and renovated
rail sections, but the situation is quite different with old tracks. If the problems of
unevenness can be dealt with adequately by improving drainage, it is considerably
more advantageous compared to massive renovation. The aim of this study is to
find out whether systematic improvement of drainage can produce significant
savings in rail network maintenance.
The study examines the problems of unevenness discovered along the Finnish rail
network, where the functioning of drainage is a major factor while seeking
solutions to the problems. This article presents the technical and administrative
problems related to drainage in the Finnish rail network.
Based on observations made so far, even basic drainage solutions are beset with
problems, since, for example, ditches are not cleaned with sufficient regularity. It
can be said already at this phase of the study that drainage maintenance should be
improved. The literature review proved that increased moisture content will
degrade soil properties, leading to permanent deformation and expose the track to
frost heave. The computational modeling of different drainage systems showed
that track moisture can be decreased by basic operations like deepening the ditches.
It also revealed that poor materials, which absorb more moisture, are very hard to
be made dry enough.
Our in-situ measurements from monitored sites revealed high moisture levels.
Based on lab tests, we found that the shear strength considerably increased when
we lowered the moisture level in static triaxial test. We also found that some real
samples of track sub-ballast can absorb water very effectively. It is probably very
hard to get such materials to work properly in a railway track. The next step in this study is to do more lab tests and measurements from monitored sites. We shall also
be making some improvements to drainage in our monitored sites, to study the
effects of drainage enhancement.