Vibrations caused by train traffic and the effect of its mitigation on the quality of living

Railway traffic induced vibrations in dwellings often cause irritation or disturb the inhabitants. Mitigation has been performed, and measurements prove their effectiveness. The effect of vibration countermeasures on the quality of living however has not been studied earlier. The objective of the study was to evaluate the effects of vibration mitigation compared to the increase of inhabitant satisfaction, would the halving of vibration levels lead to a doubling of satisfaction? The investigation was done by means of a literature study, vibration measurements and written surveys with the financial aid of the Finnish Rail Administration. The testing was carried out in Raunistula, a suburb of Turku, in Southwestern Finland. Passing along the side of the residential area, the Toijala-Turku railway line causes vibrations in the surrounding areas affecting the quality of residents’ life. To attenuate the vibration, two different structures were constructed, a sheetpile wall and a matrix of lime-cement columns. Typical to the Southwestern region of Finland, the soil in Raunistula consists of a thick layer of clay with low shear strength. This soil type allows large displacements in railway sub-structures, especially if ground supported. Additionally, the low natural frequency and damping coefficient of clay lead to minimal attenuation and widespread effects in the surrounding area. The level of vibrations and residents’ satisfaction was evaluated prior to construction. After the installation of the aforementioned barriers, a new round of measurements and surveys was performed in order to find out how the mitigation succeeded. Results were satisfactory, the greatest amount of mitigation was achieved nearest to the track and comments of a rise in the quality of living were achieved. The mitigation however was limited to a certain distance from the track. Farther away, partly due to other sources of vibrations and noise, the mitigating effect of the structures was negligible. The results of both the surveys and measurements show an improvement of 30 to 50 %, confirming the hypothesis that inhabitants' satisfaction increases as much as the intensity of vibration decreases.