Researchers test in the computer what happens in the railway line. |
The
construction of new rail lines, or the relocation of old ones
underground, has increased society’s interest over recent years in the
vibrations produced by trains, especially among people who live or work
near the tracks. Now a study headed by the Polytechnic University of
Valencia (UPV) has made it possible to estimate the trajectory of
vibrations from the point at which they are generated (wheel-rail
contact) through to the ground.
“The
model acts as a “virtual train laboratory’, meaning that, if the
parameters of the train or the track ballast are changed, it is possible
to infer the pattern of the resulting vibrations”, Julia Real,
professor of transport and railways at the UPV and lead author of the
study, tells SINC. “This is ideal for testing changes that, if they
work, could be put into practice”.
If,
for example, the data from an AVE high speed train with an aerodynamic
nose are entered rather than those from another train with different
mechanical characteristics, different vibration patterns are obtained.
The same thing happens when comparing a track without any levelling
defects with another older one, or if the condition or type of material
used beneath the sleepers are changed.
“The
results depend to a large extent on the elasticity, density and
thickness of the materials, especially the ballast (gravel that the
sleepers rest on)”, points out Pablo Salvador, another UPV researcher,
who is also a co-author of the study.
The
scientists created the analytical model using mathematical equations
that describe the frequency and number of waves. The details are
published in the Journal Mathematical and Computer Modelling.
“It’s
a fairly robust model that is relatively simple to use, and which makes
it possible to determine potential vibration levels in an area
following the introduction of a rail line, and also provides input
information for a 2D surface vibration propagation system”, explains
Salvador.
Validation on the Madrid-Barcelona line
The
theoretical results have been successfully compared with experimental
frequency and vibration duration measurements taken along the
Madrid-Barcelona high speed line. This information was provided by the
public company Ineco, which is attached to the Ministry of Public Works.
This
study is the first of a series of three, which will use the same
methodology to analyse two other rail facilities – an urban tram line
(line 1 of the FGV in Alicante) and a Spanish narrow gauge railway along
the Santander-Liérganes line.
“In
the first case, which has just been published, we focused on ‘the best’
(new vehicles and tracks meeting maximum speed and international gauge
requirements); in the second case, the urban tram calls for the greatest
possible attention with regard to vibrations, requiring extreme care
even though they have only small loads and speeds; and the third case
will look at a mixed rail operation (passengers and merchandise) making
optimum use of resources”, explains Julia Real.
“These
are three different kinds of rail facility, each having its own
structure, requirements and determining factors… but all of which are
tremendously efficient with regard to society and the environment”, the
researcher concludes.
References:
Pablo
Salvador, Julia Real, Clara Zamorano y Antonio Villanueva. “A procedure
for the evaluation of vibrations induced by the passing of a train and
its application to real railway traffic”. Mathematical and Computer
Modelling 53 ( 1-2): 42-54, January 2011.
