Empirical prediction of ground-borne vibration from railway systems
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Typ
Examensarbete för masterexamen
Program
Sound and vibration (MPSOV), MSc
Publicerad
2021
Författare
Vågfelt, Gustav
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In today’s society with the trends of urbanization and rapid growth comes an increasing
demand for fast and eco-friendly land travel, with low noise and vibration
emission. To predict ground-borne noise and vibration from railway systems, several
empirical and numerical models have been developed. Generally, soft ground
materials can generate low frequency disturbances in the vicinity of the railway.
Stiffer materials can transmit a higher frequency ground-borne noise. Investigations
in Sweden have shown that areas with non-stiff soil materials, for example very loose
clay, can produce high vibration levels at low frequencies. This is true for some of
the soil materials deposited during the melting of the last land covering ice cap,
which can be found at various sites throughout Sweden (glacial soils).
This thesis presents an investigation of ground-borne vibration prediction using an
empirical model named High-Speed 2 (HS2), developed in two major high-speed
railway projects in the United Kingdom. The relevant underlying theory and the
prediction model was studied during the initial literature review. The model was
programmed in Matlab, and has been utilized to compute predictions of vibration
levels arising at a receiver position, as a result of a train passage. A measurement
data set of train passages at a Swedish site where the ground material is constituted
by glacial clay, has been acquired and processed. This was done in order to
compare measurements and predictions for an evaluation of the model’s accuracy
under Swedish conditions. The findings indicate that the HS2 model can compute
relatively accurate vibration level spectra using the default reference data within
the model, for the studied case. The average single value difference (vertical particle
velocity at the soil surface) between vibration level of predictions and measurements
is approximately 2.0 dB, with slight over-estimation of levels for most of the studied
frequency range, 6.3 to 250 Hz. This is considered as good accuracy for general
noise and vibration assessment. However, it should be noted that these results are
based on a comparison of the model with measurement data from one single Swedish
site. Further, the model seem to produce lower levels than measurement data at
very low frequencies. It is possible that new reference source spectra and propagation
terms for soft ground materials would increase the accuracy of predictions
for low frequency vibration under Swedish conditions. This would require further
measurements for sufficient statistical confidence.
Beskrivning
Ämne/nyckelord
Ground-Borne Noise and Vibration, Railway Systems, Soft Ground Materials, High-Speed 2 (HS2) , Prediction Model, Low Frequency Vibration