Photo: Norwegian National Rail Administration
Ground-borne vibrations originating from rail traffic is a growing problem worldwide. In many countries, changing socio-economical structures have meant an increase in the mobility of the population thereby necessitating large infrastructure investments. This often entails the construction of rail based transportation systems in highly populated areas. RockDelta stone wool based track anti-vibration mats offer an efficient, durable and cost-effective solution to vibration problems encountered alongside the tracks of railways and tramways – often resulting in a considerable improvement to the quality of living in the vicinity of the track.
Consequences of Railways and Tramways in Densely Populated Areas
Offering significant advantages to individual users as well as to the community at large, the use of railways, not least high-speed railways and rapid mass transportation systems in urban and sub-urban networks, is increasing worldwide. Many cities have accordingly encountered the problem that important infrastructure projects – involving railways or tramways – come close to densely populated areas or vibration-sensitive areas.
In industrial areas, although vibrations caused by the passage of rolling stock on a railway or tramway track may not immediately result in damage to buildings and their foundations, they are known to cause delicate machinery located inside buildings to malfunction. Equally important, in residential areas, the passage of rolling stock on railways or tramways, and the resulting generation of noise and vibration, may greatly annoy the people living alongside the railways, causing everything from discomfort to an adverse impact on the quality of life often resulting in increased levels of stress during daytime and sleeping problems during nighttime.
European Union Green Paper on Future Noise Policy
According to a recent European Union Green Paper on Future Noise Policy, an estimated 1.7% of the inhabitants of the European Union – corresponding to almost 8 million persons – are exposed to a railway noise level of 65dB (A) during daytime. This level is regarded as above an acceptable level. Furthermore, an even larger amount of persons is exposed to a railway noise level of 55 – 65dB (A), which is regarded as very annoying with a harmful impact on the quality of life.
Vibration Propagation from Rails
The process of the vibration propagation from a rail track and track formation to the surrounding structures has the following phases; generation, that is, force excitation caused by the passage of rolling stock with irregular wheel geometries over imperfect rail running surfaces; transmission, that is, the propagation of waves through the surrounding soils; reception, that is, the propagating waves received as vibrations by nearby buildings – possibly amplified by these because floors, walls and windows may resonate – by people and by machinery inside these buildings; and finally intervention, that is, the mitigation of vibrations using various isolation techniques.
Anti-vibration Plates under the Track Superstructure
Related to intervention, a number of methods have been developed to help control ground -borne vibrations. One of the popular and most effective techniques remains the installation of anti-vibration plates under the track superstructure.
In ballast tracks such anti-vibration plates take the form of sub-ballast mats, and in float-ing slab-tracks they take the form of a full-contact resilient element between the concrete trough and the floating slab onto which the track is fastened. In both cases, a spring-mass system is achieved, whereby vibration isolation is achieved from frequencies approximately 1,4 times above the resonance frequency.
With stone wool based anti-vibration mats exhibiting outstanding longevity, excellent dynamic properties and surprisingly low sensitivity to all track-related environmental factors, the RockDelta product lines are uniquely positioned in the market as durable, high-efficiency, sheet-type elastic bearings for any type of track demanding a cost-effective yet highly isolating solution.
