vibration from tunnelling dr david hiller yung loo 26 th january 2015

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


Res

ulta

nt P

eak

Par

ticl

e V

eloc

ity

(PPV

)

4


Excavation of more competent chalk at Ramsgate

Vibration magnitude as PPV is determined by the geology, not the tunnelling method

Excavation of weak chalk at Ramsgate

Attenuation appears not to be significantly geology dependent over this range of distances

Res

ulta

nt P

eak

Par

ticl

e V

eloc

ity

(PPV

)

5


6


45m

0.2 mm/s2x10-4 m/s200µm/s At 45m, tunnelling vibration

would give ~200µm/s peakOr ~ 50µm/s rms

7

Residential (day)

Operating theatre

VC-A

VC-B

VC-C

VC-D

VC-E

NIST-A1NIST-A

Vibration Criteria – Where do we sit?

50µm/s

8

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-A1NIST-A

Vibration criteria – but what do they mean?

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


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


Surgeon Discipline Microscope

Vibration at perception 1/3 octave rms vel (µm/s)

Vibration at perception overall rms vel (µm/s)

Vibration a problem 1/3 octave rms vel (µm/s)

Vibration a problem overall rms vel (µm/s)

Comments

Highest† Next to

microscope base

Highest†Next to

microscope base

Highest†Next to

microscope base

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 47 101 92 121 110 Problem for fine work

Ms Pat Logan

Eye Surgeon

Leica F40 x8 magnification (c.50% of range)

61 54 72 64 70 62 85 74

Kevin O’Malley

Vascular Loops x3.5 magnification

N/A – loops used

N/A – loops used

N/A – loops used

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

Ear Nose and Throat

Zeiss set at x2.5 x 10

23 20 29 25 30 26 38 33

Ciaran Bolger

Neuro Leica M525/ULT500 *

N/A N/A N/A N/A 51 48 64 60

Gavin Quigley

Neuro Leica F40* 19 18 24 23 19 18 24 23 Problem as soon as perceptible

Michael O’Keeffe

Eye Leica F40 x9 magnification*

12 11 17 17 21 20 27 25

Marcus Timlin

Orthopedic Zeiss on lowest magnification

N/A N/A N/A N/A (98) (87) (119) (105) No problem these levels (maximum vibration achieved given in brackets)

Jim McCarthy

Cardiac Loops x3 magnification

11 N/A – loops used




Prof. Ciaran Bolger

Neuro Wild Heerbrugg (Wild M691)

17 16 21 20 78 75 92 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

vibration from tunnelling dr david hiller yung loo 26 th january 2015

Documents