1. Vibration from tunnelling
Dr David Hiller
Yung Loo
26th January 2015

2. Vibration issue Excavation and construction work would be at c.45m
What will be the effects?

3. Vibration from tunnelling
Resultant Peak Particle Velocity (PPV)

4. Vibration from tunnelling
Excavation of more competent chalk at Ramsgate
Resultant Peak Particle Velocity (PPV)
Excavation of weak chalk at Ramsgate
Vibration magnitude as PPV is determined by the geology, not the tunnelling method
Attenuation appears not to be significantly geology dependent over this range of distances

5. Vibration from tunnelling

6. Vibration from tunnelling
0.2 mm/s
2x10-4 m/s
200µm/s
At 45m, tunnelling vibration would give ~200µm/s peak
Or ~ 50µm/s rms
45m

7. Vibration Criteria – Where do we sit?
Residential (day)
Operating theatre
VC-A
VC-B
VC-C
VC-D
VC-E
NIST-A1
NIST-A
50µm/s

8. Vibration criteria – but what do they mean?
Overall figure or an octave or 1/3 octave or narrow band rms?
Over what frequency range?
Duration over which measurement should be determined?
Max-hold or time averaged rms?
Measured where – eg on the floor, on the equipment?
Worst case or a spatial average?
Single (any?) axis or resultant?
Residential (day)
Operating theatre
VC-A
VC-B
VC-C
VC-D
VC-E
NIST-A1
NIST-A

9. Vibration impacts and assessment criteria
Atomic-scale microscopy

10. Vibration impacts and assessment criteria
Vibration at source
Attenuation with distance
Transfer function – ground to building
Equipment / process sensitivity

11. Vibration criteria – establish the ambient level
50µm/s

12. Vibration Criteria for Hospitals
Tunnelling alongside and 30m below a hospital
Radiotherapy suites, scanners, microsurgery, etc all potentially vulnerable
Predict tunnelling vibration and compare with established criteria and manufacturers’ specifications
Criteria not available for all equipment or every process
Tests carried out to establish criteria where there was none

13. Vibration Criteria for Hospitals
“Theoretical models are not sufficiently reliable to predict vibration propagation from different sources of construction activities through geological formations. Therefore, predictions of vibrations and groundborne noise presented in the EIS [Environmental Impact Statement] are preliminary in nature and must be verified by field vibration measurements. Prediction models need to be calibrated against and updated based on field trials.”
Expert’s Report to the Dublin Metro North public enquiry (Massarsch, 2010:58)

14. Vibration Criteria for Operating Theatres

15. Vibration Criteria for Operating Theatres
Neurosurgeon’s observations:
At the floor natural frequency, vibration became perceptible through the microscope such that at 108 and 133μm/s (two measurement positions; rms 1/3 octave band) the surgeon would not be happy to work.
At the resonance frequency of the microscope, vibration became perceptible at around 20μm/s rms and would be clearly a problem at 33μm/s (rms 1/3 octave band).
Operating theatre

16. Vibration Criteria for Operating Theatres
Surgeon
Discipline
Microscope
Vibration at perception 1/3 octave rms vel (µm/s)
Vibration at perception overall rms vel (µm/s)
Vibration a problem /3 octave rms vel (µm/s)
Vibration a problem overall rms vel (µm/s)
Comments
Highest†
Next to microscope base
Mr O’Laoire
Neuro
Leica M525/ULT500 at c.75% of maximum magnification 47 43 56 51 81 74 92 84
Mr Colreavy
Ear Nose and Throat
Zeiss OPMI 1-FC. Magnification x2.5 44 40 52
101
121
110
Problem for fine work
Ms Pat Logan
Eye Surgeon
Leica F40 x8 magnification (c.50% of range) 61 54 72 64 70 62 85
Kevin O’Malley
Vascular
Loops x3.5 magnification
N/A – loops used
No problem at highest 1/3 oct rms vel – 90 µm/s; highest overall rms vel – 112 µm/s
Mr O’Dwyer
Zeiss set at x2.5 x 10 23 20 29 25 30 26 38 33
Ciaran Bolger
Leica M525/ULT500 *
N/A 48 60
Gavin Quigley
Leica F40* 19 18 24
Problem as soon as perceptible
Michael O’Keeffe
Eye
Leica F40 x9 magnification* 12 11 17 21 27
Marcus Timlin
Orthopedic
Zeiss on lowest magnification
(98)
(87)
(119)
(105)
No problem these levels (maximum vibration achieved given in brackets)
Jim McCarthy
Cardiac
Loops x3 magnification 15
Prof. Ciaran Bolger
Wild Heerbrugg (Wild M691) 16 78 75 87
Deep cavity simulation – spatula in mouth to test light and shadow

17. Conclusions
In many cases there are no established vibration guidelines or they are poorly understood, leading to a need to define vibration criteria
Established criteria and manufacturers’ specifications can be ambiguous in any case.
Need to know:
Vibration at source – seems to be defined by geology, so probably cannot appreciably reduce
Vibration at the instrument – measured where; which elements? Any critical frequencies?
What are the actual assessment criteria – both for operational and non-operational times
‘Not above ambient’ may be unduly restrictive
Analytical approach – works well for structural analysis (eg Extreme Light Infrastructure Laser Hall, Prague) but less well where there are complex unknowns