Ground Vibration Caused by Tunnel Construction and its Effect on an Electron Microscope

Jun Tobita1, Nobuo Fukuwa2
1

Associate Professor, Graduate School of Environmental Studies, Nagoya University
2
Professor, Graduate School of Environmental Studies, Nagoya University

Abstract
In this study, we observed the vibrations caused by the construction of a roadway tunnel excavated using
the New Austrian Tunneling Method (NATM) in an urban area. We analyzed the resulting vibrations anddisturbances and their effect on a high-voltage electron microscope (HVEM). The characteristics of theconstruction equipment, various construction tasks, wave propagation and attenuation in the soil, along withthe transmission of vibration forces to adjacent buildings were also clarified. These findings were combined
and the effects on the HVEM were examined to model vibration-induced disturbances. The accuracy of thesefindings was confirmed by comparing the results obtained with actual observations that were recorded later.
The findings of this study are expected to enhance the ability to distinguish between the many factors
involved in vibration-induced disturbances caused by equipment. The findings could also be applied tomonitoring construction activities and predicting the effects of vibration-induced disturbances onhigh-precision equipment.
Keywords: environmental vibration; tunnel construction; electron microscope; vibration measurement; prediction

1. Introduction
When constructing underground structures such as
subway and roadway tunnels, it is essential toinvestigate the influence on surface structures
resulting from tunnel construction and its related noiseand vibration. A greater understanding of these
phenomena is particularly valuable in urban areas.
Furthermore,buildings
today
often
house
high-precision equipment that can be affected by even
low levels of vibration. The characteristics ofvibrations arising from tunneling operations arestrongly influenced by the tunneling method used, thesoil conditions of the area, and the structures ofnearby buildings (Takemiya, ed., 2005, Takei et al.,2008).
In order to model vibrations and determine ways inwhich they can be counteracted and mitigated, it will
be necessary to separately consider the characteristics
of each of the different processes occurring in actual
tunneling operations. Examples of these parameters
include vibrations occurring as a result of theequipment employed and operation techniques,classification of the wave propagation in the groundContact Author: Jun Tobita, Associate Professor, Graduate
School of Environmental Studies, Nagoya University,
Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
Tel: +81-52-789-3754, Fax: +81-52-789-3768
e-mail: tobita@sharaku.nuac.nagoya-u.ac.jp(The publisher will insert here: received, accepted)

and ground wave attenuation with distance, vibration
imposed on adjacent buildings, and the effects
imposed on high-precision equipment.
Using extensive vibration measurements that werecollected during tunneling operations, this paper
clarifies the characteristics of vibrations transmitted
through the soil during expressway tunnelingexcavations in an urban area. The study focuses on theeffects of these vibrations on nearby buildings and ona typical high-precision instrument (a high-voltage
electron microscope (HVEM), H-1250ST, 1,000 kV,
CTEM/STEM). The vibration measurements werecarried out using a large array of sensors that wereplaced at various locations inside the tunnel, buried in
the ground, installed in the building housing the
HVEM and attached to the HVEM itself. Closed
circuit television (CCTV) cameras were installed tosimultaneously observe tunneling operating conditions
and the HVEM monitor in order to provide additional
information about the relations between tunneling
operations, vibrations, and disturbances to the
instrument. We then attempted to predict the vibration
characteristics that would occur as the tunnel-boringmachine passed directly beneath the HVEM, andsubsequently compared these modeled predictions
with the results of actual observations. These findings
indicated that the present approach for modelingvibrations resulting from underground construction
operations is effective.

Journal of Asian Architecture and Building Engineering/May 2009/111

1

2. Outline of Tunneling Operations and Vibration
Measurements
This study monitored a tunneling project conductedbeneath the northern end of the Higashiyama Campusof Nagoya University that will eventually form part ofa Nagoya metropolitan expressway. The New Austrian
Tunneling Method (NATM) was used to construct atunnel with a limited thickness of covering soil and awide cross-section. The surface area above and oneither side of the tunnel consists of a residential
district and various university research facilities
employing high-precision equipment, including an
HVEM laboratory; however, it is feared that thevibrations caused by the tunneling and tunnel traffic
could disrupt activities at those research facilities.
Figure 1 shows the general plan and cross-sectionalviews of the tunnel and nearby university structures.
The tunneling operation proceeded from west to east
(left to right in the figure). First, two smaller tunnels(known as drifts) were excavated on each side of the
proposed path of the main bore, which was excavatedbetween the drifts. The area consists of soft topsoil
from the surface to −5 m, sand and gravel from −5 mto the upper half of the tunnel (about −15 m), and clay
and sand below that level. The pilings of the nearbybuildings are supported by a layer of hard sand andgravel.
Measurements were carried out in the adjacentstructures and in the soil along Transects A, B and C
during the tunneling progress. The measurements
along Transect C provided data related to the building

Transect B

Transect A

Main tunnel

DriftsDriftswhere the most precise HVEM maintained in thiscomplex was located. At its closest, the straight-line
distance from the building to the tunnel was about 25m.
Vibration sensors were placed in the tunnel, buried
underground, installed at ground level, and at sensor
points located in the building. (Surface andunderground points are shown by open and closed
circles, respectively.) The sensors used wereservo-type accelerometers on Transects A and C(Fukuwa et al. 1997) and temporary moving-coil typemicrotremor sensors on Transect B (see section 4
below).
Figure 1(d) shows a close-up view of the HVEM
and its vibration isolation table, which is supportedwith rubber bearings and viscous dampers. Sensor C6
was on the table. The mass foundation of the isolation
device is supported by 12 piles measuring 9 m within
the dense gravel layer.
Closed circuit TV cameras were placed in thetunnel and at the HVEM so that both locations could
be observed simultaneously in a split image on asingle monitor. Photo 1 shows the monitor screen. The
upper images show the tunnel interior, the lower left
image shows vibrations in the tunnel and in the soil,
and the lower right image shows the screen of the
HVEM. These streaming images were recorded andwill be used for further investigation into vibrations
produced by activities and equipment employedduring tunnel construction, and to determine howthese factors affect HVEM operation.

Transect C

A2

A1

Long
forepoles

C0

A0
B1
A3

C3

C1

C4 C2

B2
B3

Concretesidewall

EM
C6
C5

B4

Ground surface &indoor floor sensors

DriftsPilings

Underground sensors(b) Cross-section of tunnel and soil structure

EMs & other devices(a) Locations of roadway tunnel with adjacent buildings and sensors

RC 2-story building

SRC 6-story building

High-voltage
electron microscope

RC 1-story buildinga.

Clean room

Semiconductor
production equipment

C6

A2

B1

A3

B2

B3

B4

Clay
GravelA0

C0
A1(c) Cross-section and sensor locations along the three instrumentation Transects.

C3

b.

C5

Gravel

C6

C4

c.
d.

C2

a. EM isolated frameb. EM bodyc. EM foundationd. Pileclay
gravel
C1 sand(d) The HVEM setup

Fig.1. Outline of the tunnel project, nearby buildings, HVEM setup, and the sensor networks

2 JAABE vol. 8 No. 1 May 2009

Jun Tobita

3. Characterization of Vibrations Caused byTunneling Equipment
The vibrations caused by various kinds of tunneling
equipment were compared by conducting observations
along Transect C, immediately adjacent to the tunnel.
Figure 2 shows the three kinds of heavy equipment
during operation and their accompanying vibration
records. The oval circles on parts of the vibration
record indicate the vibrations caused by equipment. It
was not possible to determine which equipment was
being used solely by looking at the raw vibration data.
However, observations from the CCTV camera
installed in the tunnel (as mentioned in Section 2 andshown in Photo 1) enabled the observer to identify theequipment being used. Figure 3 presents the Fourier
spectra of the different operations at the A1 sensor.

Photo 1. Split screen showing tunnel construction activities,
seismic waveform and electron microscope monitor

ニブ ラー
Nibbler＜ ニブラーによる支保 工引 っ張り作業 時 ＞

Vibration during removal of timbering by nibbler●●●●●●●●●●● ●●バ ックホー

3
1 .5
0
-1 .5
-3

0

10

20

t im e( sec )

30

40

50

40

50

40

50

＜ バックホーによる土
砂の 掘削of時＞
Vibration during excavationsoil by backhoeacc.(gal)

Backhoeacc.(gal)

●

2
1
0
-1
-2

0

10

20

t im e( sec )

30

＜ キャリ
アダンプ走行時＞of tracked carrier dump
Tracked carrier dump
Vibration
during travelacc.(gal)

キャリアダンプ

1
0 .5
0
-0 .5
-1

0

10

20

t im e( sec )30

Fig.2. Characteristics of vibration caused by different construction equipment
Excavation of main tunnel
Carrier dump transit
Excavation of drifts(a) Parallel to tunnel axis(b) Perpendicular to tunnel axis(c) VerticalFig.3. Acceleration spectra during equipment operation along Transect A (Sensor A1)
C1, Excavation of drifts
A1, Excavation of main tunnel
A1, Excavation of drifts

A1, main tunnel
C1, main tunnel
A1, drifts
C1, drifts

Microtremor

Microtremor

Microtremor(a) Parallel to tunnel axis(b) Perpendicular to tunnel axis(c) Vertical to tunnel axis
Fig.4. Acceleration spectra during excavation of drifts and main tunnel measured at Transects A (A1) and C (C1)

JAABE vol. 8 No. 1 May 2009

Jun Tobita

3

These spectra provided clear indications of both theequipment in use and the difference of vibration
characteristics along three axes.
For example, pulse-like vibrations caused by
excavation (Fig. 2) show wide frequency range in Fig.
3. Alternatively, long duration noises caused by the
tracked carrier dump (which is a dump truck equippedwith caterpillar tracks, as shown in Fig. 2) haverelatively low amplitude even though a clear peakexists at around 20 Hz. As a similar peak appears at
different frequencies depending on the travelingvelocity and ground surface conditions in the tunnel, it
was considered likely that the peak was caused byhigh frequency mechanical noises, most likely emitted
from the caterpillar tracks of heavy construction
equipment traveling over rough surfaces.
Figure 4 provides comparisons of the vibrations
observed on Transects A and C during excavation of
the drifts and the subsequent main tunnel. The
vibrations were more intense during the digging of themain tunnel, although the spectra were relatively
similar since the construction equipment activities

Sourcewere similar. The vibration characteristics obtained
along Transects A and C during the operation of otherearthmoving equipment were both similar. It isapparent that digging resulted in vibrations more than
10 times as intense as those experienced when theequipment was not in use.
The long-term observations of the tunneling
operations showed that the amplitude and frequency
were generally constant for all vibrations. The resultsof these measured vibration characteristics can beused when observing other projects of this type in the
future.
4. Wave Propagation in Soil
We will now examine how the distinctive
components of the most common vibrations describedin the previous section propagate through the soil.
Figure 5 shows the waveforms and three-dimensional(3D) orbits of particles at points B1 – B4 on the
ground surface along Line B. These are examples ofrecords taken at the location marked with × near point
B1 during excavations 23 m below ground level. The

B1

B1

B1

B2

B2

B3

B3

B4

B4

(a) r direction(b) θ direction
Fig.6. Cross correlation functions along Transect B
Average of peak velocity(mkine)Eq. (1)(a) Transect B
B1
B2

B2
r direct.
θ direct.
φ direct.

B3

B4

Excavation stop
(microtremor in r direct.)Distance from excavation point (m)Average of peak velocity(mkine)C3B3(b) Transect C

C4

C1

r direct.
θ direct.
φ direct.

C2
r direct.
θ direct.
φ direct.

Eq. (1)

B4Distance from excavation point (m)Fig.5. Three-dimensional particle motion of observation
points on Transect B

4 JAABE vol. 8 No. 1 May 2009

Fig.7. Attenuation of maximum vibration amplitudewith distance on Transects B & C

Jun Tobita

excavation mainly propagate in the form of bodywaves. This was also noted in the measurements on
Transect C.
Figure 7 shows the characteristics of wave
attenuation with the average peak velocities observedon Transects B and C. The vertical axis represents thehighest mean peak velocity and the horizontal axis
represents the distance from the vibration source. The
observed values on Transect B were joined with lines
in the order B1 – B4, and were compared with thevalues observed during the machine stops marked by×. The points on the surface and underground along
Transect C are also connected. The theoreticalattenuation for body waves,

3D particle trajectory is projected onto the X-Y plane,
the Y-Z plane and the Z-X plane. In this figure, it canbe seen that the direction from any point toward more
intense vibration is the same as the direction toward
the source of vibration. However, this correspondence
between directions is attenuated as the distance fromthe vibration source increases.
The directions of vibration of the soil particles
shown in Fig. 5 were resolved into the r direction
toward the source and the θ direction orthogonal to r.
The particle motions at points 1 through 4 wereanalyzed to find waves showing strong mutual
correlations in the r and θ directions and propagationin the appropriate order from points B1 to B4. Figure
6 shows cross correlation functions using point B2 as
the reference. The wave velocity in the r direction
corresponds approximately to the longitudinal wave
velocity (1000 m/s), and that for the θ direction, to thetransverse wave velocity (400 m/s). These findings
show that the vibrations occurring during tunnel
Amplitude

A/A0 = exp(-2πfhr/V)/r,(1)

is also plotted here, where A0 is the vibration
amplitude at the source, A is the amplitude at distancer, and f, h and V are the vibration frequency, internal

Amplitude

Amplitude

1st floor/Underground(C5/C2)
1st floor/Ground surface(C5/C4)(a) r direction(b) θ direction
Fig. 6. Cross Correlation Functions from Line B(a) Parallel to tunnel axis(b) Perpendicular to tunnel axis(c) Vertical to tunnel axis
Fig.8. Transfer functions and coherences concerning building containing HVEM
Amplitude32

振幅比●●●●●●●●●●●●●ジ ャ イ ア ン ト ブ レ ーカ

Excavation

ベース
プレート

2.5

●

基礎柱
電子顕微鏡
b.

1

バッ
ク ホー
Backhoe

Giant breaker

c.

C6/C5

1.5

本体

0.5
0
0

5

10
15
20
frequency(Hz)

25

1.2

Backhoe struck timbering

キャcarrier
リ ア ダンdump
プ
Trackedmkin*sec

1
0.8

C6

30

(b) EM foundation-table transfer function

Traffic

a.
防振ゴム

吊り下げ
架台

C5
d

電子顕微鏡
基礎

a. Isolation rubberb. EM bodyc. Hanging framed. Foundation

Excavating soil

Fig.
0.6 7. Attenuation of Maximum Amplitude ofTracked carrier dump motion
0.4 Vibration with Distance on Lines B & C
0.2
0

0

5

10

15

20

25

(a) Typical waveform of acceleration on isolation table

30

0

5

10
15
20
frequency(Hz)2530(c) Fourier spectrum of vibration on isolation table

Fig.9. Vibrations experienced by the HVEM installed on an isolation table

JAABE vol. 8 No. 1 May 2009

Jun Tobita

5damping and elastic wave velocity, respectively. Here,the latter values were h = 0.02 and V = 400 m/s. These
results indicate that, as expected, the main waves were
the body waves propagating through the soil. Thisfinding clarified that the attenuation characteristics
could be predicted by equation (1) for distancederived for body waves.
5. Vibration Input on Buildings
We will now consider the characteristics of thevibration components propagated through the soil
from the tunnel and exerted as forces on buildings.
Figure 8 shows the transfer functions in all three
dimensions at the foundation of the HVEM on the firstfloor. Measurements were taken between theunderground sensor (C2) along Transect C, under thefloor of the HVEM (C5), and at a point between the
ground surface (C4) on Transect C and the floor underthe HVEM (C5). The horizontal components wereconsiderably amplified at the natural frequency of thebuilding structure, while the higher-frequency
components were reduced in the building. Conversely,
the vertical vibration did not show significant
amplification. The observed attributes of the vibrationin this building differed somewhat from thoseobserved in other buildings, although some variation
could be expected to arise due to differences in thecondition and foundations of the structure of thebuilding.
6. Interference with the Electron Microscope
Figure 9(a) shows the observed waveforms and Fig.
9(c) shows the Fourier spectra of the vibrations
excited on the top surface of the vibration isolationtable beneath the HVEM. These waves and spectra
were predicted by the transfer function between thevibration isolation table and the first floor of thebuilding, as shown in Fig. 9(b). By multiplying the
input waves on the first floor of the building(discussed in the previous section) with the transfer
function, we able to predict the waveforms andfrequency spectra arriving at the HVEM.
A small shaker for vibration testing was attached tothe body of the HVEM and its amplitude andfrequency were varied to determine the response interms of the interference observed on the monitor of
the instrument. Figure 10 shows the results of theseobservations, with the  symbols in the figure
indicating the levels of vibration at which interference
was first manifested, and the × symbols showing wheninterference was clearly present. The four plots show
the amplitudes and vibration spectra on the HVEM
predicted by the complete set of vibrations associatedwith the construction activities addressed in this report,
including the vibration source characteristics of theoperations described in Section 3, the attenuation with
distance described in Section 4, the soil to building
input characteristics described in Section 5, and thebuilding floor to the isolation table characteristics
described in Section 6.
While larger vibrations were detected closer to thesource, the observed spectra were frequency
dependent. Vibrations were also more intense during
excavation of the main tunnel (Fig. 10(b)) compared
to construction of the drifts (Fig. 10(a)). The sectionsof the spectra where the acceleration exceeded thevalues denoted by the  symbols indicate whereinterference occurred in the HVEM at a given distance.
The levels of vibration () were particularly low at 3
Hz and 5 Hz, indicating increased sensitivity tovibration at those frequencies. Figure 9(b) indicatesthat 5 Hz was the natural frequency of the HVEM
isolation table. Thus, by examining Fig. 10, it waspredicted that the HVEM would be disturbed byvibration while excavations were conducted within 60
m of the HVEM for the main tunnel, and within 40 m
for the drifts.
Finally, Fig. 11 shows the predicted and observed
vibration spectra at the location physically closest to
the HVEM. These vibrations exceeded the predictedlevel resulting in interference to the HVEM at. In
addition, the observations confirmed that the images

Predicted
Observed(a) During excavation of drifts(b) During excavation of main tunnel
Fig.10. Level of interference due to acceleration of the HVEM (×: Clear interference
: Not clear) and predicted acceleration spectra for distance from operations

6 JAABE vol. 8 No. 1 May 2009

Fig.11. Predicted and observed HVEM
acceleration spectra during closest
approach of digging operation

Jun Tobita

provided by the HVEM were affected at thisfrequency. The reason the observed values were lower
than the predicted values was thought to be because
the excavation crews had employed measures tomitigate as much vibration as possible, resulting in thepredicted results differing only slightly from thoseobtained from actual observations.

Japanese)
3) Fukuwa, N., Tobita, J. and Nishizaka, R. (1997) On-line
monitoring system for environmental vibration using local area
network, J. of Technology and Design, AIJ, No. 5, 158-162 (inJapanese)

7. Conclusions
This research examined vibrations arising from the
excavation of roadway tunnels excavated using the
NATM and revealed details about the equipment used
for the tunneling work (the sources of the vibrations),
the characteristics of the vibrations produced, wave
propagation characteristics and their attenuation overdistance. The study also examined the vibrationstransmitted to buildings, vibratory forces exerted on
an HVEM, and the interference to HVEM images.
These factors were then combined to predict
disturbances to the HVEM before being compared toactual data.
Several innovations were employed in thisprediction method; for example, construction
activities in the tunnel were monitored using CCTV
cameras while the characteristics of the vibrationstransmitted between each stage (from the source to theHVEM) were observed with sensors placed
underground and in various other locations. This
meant that the cause of these vibrations could bedetermined by observation at the time the disturbances
affected the HVEM monitor.
The vibration disturbance predictions were greatly
affected by the vibratory characteristics of the
excavation activity, the soil, the building and the
HVEM. Nevertheless, by applying the methods
employed in this study, it will be possible to makeaccurate predictions of this type in the future.
Furthermore, such monitoring methods also allow us
to accurately clarify disturbances and damage causedby vibrations.
Acknowledgments
This project was performed in cooperation with
Nagoya Expressway Public Corporation, theHigahiyama Tunnel Construction Joint Venture, theNagoya University Vibration Countermeasure
Committee, the Nagoya University High Voltage
Electron Microscope Laboratory, and the Nagoya
University Vibration Monitoring Laboratory. Staff
members and students of the Department ofArchitecture at Nagoya University, performed
numerous observations and analyzed large amounts ofvibration data.
References
1) Takemiya, H. ed. (2005) Environmental vibrations – Prediction,
monitoring, mitigation and evaluation. C.H.I.P.S.
2) Takei, Y., Fujii, K., Izumi, Y. and Nakai, S. (2008) A study on
propagation of traffic vibration from tunnel to near building, J. ofEnvironmental Engineering, AIJ, Vol. 73 No. 627, 559-566 (inJAABE vol. 8 No. 1 May 2009

Jun Tobita

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