Ground Borne and Structural Vibration
What is Ground Borne and Structural Vibration?
Ground borne vibration is vibration that is passed into the ground from sources such as railways and roads, and is usually a low frequency vibration. This vibration can be transmitted over significant distances depending on the source and can then pass into the structure of a building where it can affect both the occupants of the building and the building structure itself.
How is it caused?
Ground borne vibration is generated by sources such as road vehicles and trains or by processes such as piling and blasting. In all of these cases the ground borne vibration is transmitted from the source into the ground. The make up of the ground then affects how the vibration is transmitted through the ground and into nearby buildings.
What are the Effects?
Ground borne vibration can have significant environmental impact on nearby buildings. Inhabitants can perceive vibration either directly as motion in floors and walls or via indirect means such the vibration being re-radiated as noise.
Once in the building structure the vibration can cause disturbance due to the movement of household objects, especially mirrors, or by the rattling of windowpanes, glassware and crockery. In extreme cases the buildings could suffer structural failure due to the effects of vibration.
In all these cases the problem of ground-borne vibration is important at frequencies typically up to 200-250 Hz. Vibration at higher frequencies is generally attenuated rapidly with distance during transmission through the ground.
For a ground with soft clay or silt ground-borne vibration may produce annoyance to people in buildings more than 200m away from tracks.
How can we help?
Dragonfly Acoustics can help by predicting the levels of vibration, which will be caused by or experienced by a particular development. We can assist by measuring levels produced by temporary operations such as piling in order to ensure that levels do not exceed prescribed limits and cause annoyance or structural damage. Finally, where it is believed that structural damage has occurred, we can assist in assessing what may have caused the damage and establish how the vibration was transmitted.