Vibration

Biospheric Engineering Ltd. provide a comprehensive vibration monitoring service for long term (traffic induced) and short term (blasting/pile-driving) vibration. Our equipment provides full tri-axial mode analysis and is calibrated by a NIST accredited laboratory.

General Information on Vibration

Complaints about vibration caused by traffic, pile-driving, and blasting are very widespread. Such complaints are often accompanied by reports of damage, e.g. cracks, to properties. Damage to buildings can occur in serious cases, but frequently the direct causes of complaint are  disturbance from windows and crockery rattling, startle or alarm at sudden impacts, or householders' fear of damage to their own property. The effects of ground-transmitted vibration are therefore not simple, but are so extensive that an accurate means of assessment is required.

The internationally recognised criteria for assessing vibration impacts is peak particle velocity measured in three orthogonal directions (x,y and z axes) and is measured in millimetres per second (mm/s).

For blasting induced vibration the US bureau of mines have set a threshold of 50 mm/s as the safe value for residences but this value has been considerably reduced to allow for older building stock and poor construction practices. 

Typical values of 30 mm/s can be tolerated by well-bracede structures made of heavy structural elements and frames. This is much higher than the figure which the human body is sensitive to. The human body is capable of perceiving vibration levels as low as 1-2 mm/s in the vertical direction. A balance must therefore be made on the potential impact of vibration from any particular operation.

The Environmental Protection Agency and An Bord Pleanala both operate to a standard figure of 12 mm/s but can lower this figure for particularly sensitive locations such as close to a micro-electronics manufacturing plant where very tight tolerances on the manufacture of computer chips can be severely impacted by groundbourne vibration. 

Traffic induced vibration close to a busy road is often confused with the low frequency noise from the traffic but vibration levels are typically of the order of 3-5 mm/s.