An upper bound which may provide a useful first estimate for the prediction of the vibrating levels likely to be generated by future mechanised bored tunnelling works can be obtained from the equation:`\nu_(res)=180 r^(-1.3)`
Because TRL Tunnelling equations 24 and 25 are derived from a limited range of materials it is possible that they may under estimate noise levels caused by tunnelling is stronger rocks and from very high energy sources such as hydraulic hammers. Therefore care should be taken in their application in these circumstances. Similarly care should be taken in extrapolating these relations over a wider range of distances than that covered by the data from which they have been derived.
Source: Transport Research Laboratory Report 429 Groundborne vibration caused by mechanised construction works (2000), Equation 24