Introduction |
The Tokaido Shinkansen opened in 1964 as the world’s first
high-speed railway. It is a key transport artery connecting
Tokyo, Nagoya, and Osaka and it has evolved into a
sophisticated, high-speed railway by refining service in
areas such as safety, punctuality, convenience, ride comfort,
and environmental friendliness. The evolution was supported
by various technological developments.
The tsunami after the Great East Japan Earthquake on
11 March 2011 caused huge damage to conventional railway
lines along the Pacific coast of Japan’s Tohoku region. Since
an earthquake in the Tokai region or a triple earthquake in the
Tokai, Tonankai, and Nankai area could cause a tsunami of
the same size, the disaster preparedness of railways in these
regions must be studied. This article reviews earthquake
countermeasures for the Tokaido Shinkansen.
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Continuing Evolution |
Since JR Central was established in 1987, much work has
been done on increasing speeds through introducing new
rolling stock; conserving energy; improving ride comfort;
enhancing transport capacity by opening new shinkansen
station in Shinagawa; improving convenience; introducing
new ATC; and securing safe and stable transport by
aseismic reinforcement of structures. Services on the Tokaido
Shinkansen have been greatly improved, cutting the fastest
trip between Tokyo and Shin-Osaka to 2 hours 25 minutes.
Some 400 daily operations on the Tokaido Shinkansen arrive
with an average delay per train of 0.4 minutes and there has
never been an accident resulting in a passenger fatality
(Figure 1).
These improvements have been achieved by pro-active
measures with the top priority on securing safe and stable
transport. In countermeasures against natural disasters, for
example, works such as slope protection has helped achieve
resistance to heavy rainfall. In earthquake countermeasures,
civil-engineering structures have been reinforced using
aseismic design. To stop trains quickly in an earthquake, the
Tokaido shinkansen EaRthquake Rapid Alarm System (TERRAS)
and other systems have been introduced. Total investment
since 1987 and including FY2012 to support safe and stable
transport has reached \2.7 trillion with approximately \150
billion invested annually in recent years (Figure 2).
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Figure 1: Changes in Delay per Train
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Technology Developments at Komaki Research Centre |
Railway operations depend on people with different skills
working diligently together. Securing safety and enhancing
future business depends on improving technical abilities. To
achieve this goal as well as train and educate employees,
JR Central established its own R&D facility in Komaki City,
Aichi Prefecture, in July 2002. The Komaki Research Centre
covers a wide area and incorporates large test machines
(Figure 3) as well as full-scale viaducts, embankments, and
other civil-engineering railway structures. These have been
used to develop the series N700A shinkansen rolling stock,
to improve maintenance and management of structures, and
to develop countermeasures to natural disasters, such as
earthquakes and heavy rainfalls.
The N700A development included studies using the
Vehicle Dynamic Simulator on introducing a body inclining
system to improve ride comfort when running through curves
at 270 km/h. (Figure 3, left). A Rolling Stock Field Test
Simulator (Figure 3, right) was also introduced in April 2008 to
re-create running of shinkansen rolling stock while stationary.
It works by operating rolling stock on track wheels to simulate
rails and reproduces running conditions by simulating various
vibrations. Efforts are underway to optimize safety, stability
and ride comfort, while cutting weight and conserving energy.
In addition to test experiments, unique simulation
technologies are being developed, including dynamic
simulation that models running trains, tracks, and structures
and for simulation of damage to reinforced concrete.
Another characteristic of the Komaki Research Centre
is that it is in an environment where general issues that
encompass the fields of transport, rolling stock, ground
facilities and track, and electricity can be actively worked
on. A major result has been development of derailment
and deviation prevention measures drawing lessons
from the Joetsu Shinkansen derailment during the Mid
Niigata Prefecture Earthquake in October 2004. As a
new countermeasure against earthquakes for the Tokaido
Shinkansen, devices are being studied that prevent as much
as possible train derailment and deviation from tracks in
an earthquake and secure running safety for trains. Based
on those results, countermeasure constructions for railway
facilities such as track, embankments, and viaducts
and for rolling stock are being realized, and various
countermeasures are currently being taken.
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Earthquake Countermeasures for Tokaido Shinkansen |
Overview
One of the most important measures for supporting
safe and stable transport by the Tokaido Shinkansen
is countermeasures against earthquakes. Earthquake
countermeasures for civil-engineering structures on the
Tokaido Shinkansen have been implemented steadily from
1979 in the Japanese National Railways (JNR) era. Most
of those have been completed for areas where long-term
blockage could occur as a result of the Level-2 (extremely
rare earthquake motion defined in Japanese seismic design
codes) seismic motion of the Great Hanshin Earthquake and
the seismic motion of the theoretical Tokai Earthquake that
was simulated in 2003.
After the Joetsu Shinkansen derailment during the 2004
Mid Niigata Prefecture Earthquake, JR Central studied new
earthquake countermeasures mainly at the Komaki Research
Centre to prevent derailment and spread of damage caused
by deviation.
The result was new installation of dual-redundant
derailment and deviation prevention methods, consisting of
derailment prevention guard deviation-prevention stoppers,
and countermeasures to control large displacement of
structures and tracks.
Earthquake countermeasures from the early days of the
Tokaido Shinkansen can be separated into the following
two categories: aseismic reinforcement of civil-engineering
structures, and measures to stop trains quickly before the
main strike.
Aseismic reinforcement of civil-engineering structures
Measures before Great Hanshin Earthquake
Following the 1978 Miyagiken-oki Earthquake, the Act on Special
Measures Concerning Countermeasures for Large-Scale
Earthquakes specified ‘areas subject to intensified earthquake
countermeasures’ for 214 km between Shin-Yokohama and
Toyohashi on the Tokaido Shinkansen. Aseismic reinforcement
(Table 1) was conducted on embankments (17.9 km), behind
bridge abutments (159), on retaining walls (3.6 km), on slope
faces (22 locations), for bridge collapse prevention (3033
locations), on viaducts (144 locations), on bridge piers and
abutments (55), and in tunnels (18.2 km).
Measures after Great Hanshin Earthquake
• Aseismic reinforcement of reinforced-concrete viaducts
During the Great Hanshin Earthquake, reinforced
Concrete columns of the San’yo Shinkansen viaduct
suffered severe shear and flexural failure, resulting in
viaduct collapse (Figure 4). Recovery restoration from
the flexural failure took much less time than the 3
months required to recover from the damage caused by
shear failure.
The Tokaido Shinkansen was fur ther from the
epicentre and only suffered relatively minor damage.
Countermeasures taken in light of this earthquake
involved jacketing its shear-critical concrete columns
in steel (Figure 5). All 17,600 susceptible columns had
been remediated by 2008. The effectiveness of steel
jacketing was validated by numerical analysis along
with load testing on models of standard reinforced concrete
viaducts. Shaking tests of 1/5-scale models of
reinforced-concrete viaducts proved the resistance to
Level-2 seismic motion (Figure 6).
Meanwhile in May 2003, the Cabinet Office announced
the predicted seismic acceleration of the theoretical
Tokai Earthquake. Since movement in excess of Level
2 is predicted for areas struck by the theoretical Tokai
Earthquake, the aseismic performance of flexure-critical
columns was also raised and another 2000 flexurecritical
columns on the Tokaido Shinkansen were
reinforced from 2005 as an extra measure
At locations under viaducts where
reinforcing using steel jacketing was
difficult, such as stations, pre-assembled
steel plates and damping braces were
used after confirming performance
equivalent to the standard jacketing
method (Figure 7). In total, some 19,600
reinforced-concrete viaduct columns
were reinforced.
• Aseismic reinforcement of reinforced-concrete bridge piers
About 1100 shear-critical, reinforced-concrete
bridge piers were reinforced
after 1995 in addition to the 55 piers
where countermeasures had already
been made since 1979. Further
countermeasures are now underway
(planned completion in 2014) on some
200 flexure-critical bridge piers that are
predicted to fail if hit by the theoretical
Tokai Earthquake. The aseismic
reinforcement uses reinforced-concrete
and steel plates.
• Aseismic reinforcement of embankments
Embankments failed extensively in
the Niigata (1964), Tokachi-oki (1968
and 2003), and Mid Niigata Prefecture
earthquakes (2004) (Figures 8 and 9). The
failures were classified by experiments
on model embankments, and other
tests to propose reinforcement methods.
Based on the new type A and B
failure proposals, major damage was
predicted, requiring long periods before
service restoration, so countermeasures
were taken from 1979 on sections
covering about 17.9 km (Table 2).
Moreover, additional countermeasures
were completed on about 6.5 km of
the Tokaido Shinkansen from 2005 to 2009 to prevent
major damage requiring long service-restoration
times. With that, countermeasures against the above
two failure proposals were completed. In areas where
the theoretical Tokai Earthquake would cause major
damage, destruction to type-C and D embankments in
Level-2 seismic motion is expected. Within that area, we
selected a further 2.9 km where Level-4 deformation is
predicted. The area has been the target of additional
countermeasures since 2008 (planned completion
in 2013). The effectiveness of sheet piling cofferdam
construction has been modelled; sheet piling cofferdam
is the standard aseismic reinforcement method for
type-A and B failures. An overview of the construction
is shown in Figures 10 and 11 along with photographs
of completed construction.Sheet piling up to 3 m in
the liquefied layer directly below the embankment
has proved effective for embankments on ground
experiencing liquefaction in type-B failures.
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Figure 2: Capital Investment in Safety
Figure 3: Vehicle Dynamic Simulator (left) and Rolling Stock Field Test Simulator (right)
Table 1: Earthquake Countermeasures in Areas Subject to Intensified Measures against Earthquake Disasters (1976-96)
Figure 4: Damage to Reinforced-Concrete Viaducts in Great Hanshin Earthquake
Figure 5: Standard Reinforcing Method for Viaducts
Figure 6: Shaking table testing of 1/5-Scale Model Reinforced-Concrete Viaducts
Figure 7: Special Reinforcement Methods for Reinforced-Concrete Viaducts
Figure 8: Circular Slip Including Support Ground
Figure 9: Levee Body Longitudinal Cracking Due to Liquefaction of Support Ground
Table 2: Embankment Failure Forms and Reinforcement Methods
Figure 10: Confirmation of Reinforcement Effects by Model Experiments
Figure 11: Aseismic Reinforcement Method for Embankments
Figure 12: Tokaido Shinkansen Earthquake Rapid Alarm System (TERRA-S)
Figure 13: Earthquake Countermeasures for Tokaido Shinkansen
Table 3: Measures to Prevent Derailment and Deviation for Tokaido Shinkansen
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Measures to stop trains quickly
Measures to stop trains quickly in an
earthquake are composed of coastal
seismometers (from 1965), TERRA-S (from
1992), and earthquake early warnings from
the Meteorological Agency (from 2008).
The TERRA-S system uses remote
seismometers to detect the first small
primary waves (P-waves) and calculate the
earthquake size and epicentre in about 2
seconds (Figure 12). Both the TERRA-S
(at 21 locations) and coastal seismometers
(50 locations) issue immediate warnings
when the safe threshold is exceeded, and
cut power from substations to bring running
shinkansen to an emergency stop—
hopefully before the main wave strikes—
and increasing safety. Following the 2011
Great East Japan Earthquake, P-wave
detection warnings on coastal seismometers
have been augmented and functionality
in terms of multi-plate earthquakes has
been strengthened, increasing safety. In
measures for rolling stock, train emergency
braking performance has been increased.
Work is also underway to reduce the series
N700 braking distance.
Measures to prevent Tokaido Shinkansen derailment and deviation
Following the Joetsu Shinkansen derailment during the
Mid Niigata Prefecture Earthquake, JR Central examined
new derailment countermeasures from four perspectives
(Figure 13 and Table 3), based on items such as the Joetsu
Shinkansen derailment conditions and Tokaido Shinkansen
track structure and layout. The perspectives are derailment
prevention guards, ballast flow out, embankment subsidence,
and viaduct unevenness and displacement (Table 3).
• Derailment prevention guards
These guards are positioned parallel and close to the
track rails to prevent derailment as shown in Figure
15. There are various designs but the convertible type
was used for ease of maintenance (Figure 14). Tests
confirmed their effectiveness against rocking derailment
like that in the Mid Niigata Prefecture Earthquake and
maintenance problems on main-line tracks.
The effectiveness for rocking derailment was confirmed
for various seismic waves using full-scale tests on actual
bogies (Figure 16). Among the shakes in the tests, 1.0
time waveform in the displacement of the theoretical Tokai
Earthquake was used. The maximum lateral acceleration
and displacement of the waveform is 1,300 gal and
333mm, respectively. Vibration tests on a 1/5-scale model
confirmed the effectiveness against various waves, which
cannot be recreated using full-scale tests due to device
constraints. Derailment prevention guards are effective
up to 1.4 times the displacement amplitude waveform in
the theoretical Tokai Earthquake. Moreover, to confirm
the effect that running speed has on the derailment
mechanism, we performed 1/10-scale model vibration
tests on roller rig. As the adhesion between the wheels
and rails decreased as speed increased, we confirmed
that there is no difference in the derailment mechanism
during an earthquake between a vehicle running at high
speed and a stationary one, although the derailment itself
occurs more easily when a vehicle is running. Moreover, we
built a simulation model using data from full scale tests on
actual bogies and confirmed that the main cause of rocking
derailment in an earthquake is a lateral motion but not a
vertical one.
Installation tests on main-line track (Figure 17) showed no
problems with installing derailment prevention guards nor
with running of trains after installation. Checks more than
1 year after installation showed no change in position
due to running of trains, etc. Moreover, there were no
functional problems in terms of track circuits and signals.
Effectiveness, ease of installation, and maintenance all
proved satisfactory.
• Ballast flow out
The Tokaido Shinkansen uses ballasted track.
Ballast moves during an ear thquake, deforming
the track configuration and causing buckling. Earlier
countermeasures to ballast flow out use concrete
curbs weighing 150 to 200 kg each,
positioned on the outside of tracks like
a retaining wall.
For derailment prevention guards to
function, sleepers on ballasted track
must not suffer lateral displacement
of more than 30 mm. That target
value is set based on the maximum
displacement of sleepers in the
range at which derailment prevention
guards were confirmed to function in
vibration tests using actual bogies for a
theoretical earthquake (Level-2 seismic
motion and seismic motion of the
theoretical Tokai Earthquake). Moreover,
this countermeasure keeps lateral
displacement of sleepers to 30 mm and
maintains track form. However, heavy
curbs are hard to handle with accuracy
and the track must be closed during
construction. To solve these problems
we developed a new, efficient method
using 25-kg geotextile bags piled
on the slope and secured with driven
reinforcement bars (Figure 18). Full-scale
shaking tests proved this method
has the same earthquake resistance as
conventional concrete curbs (Figure 18).
• Embankment subsidence
If embankment subsidence in an
earthquake can be kept to less than 20 cm,
deformation of more than 20 cm, which is
equivalent to the height of sleepers, will
not occur when combined with ballast
flow out countermeasures because the
track configuration is maintained. We
chose soil covering/nailing to constrain
embankment deformation due to slope
shoulder subsidence at locations subject
to Level-2 seismic motion, and
Level-3 deformation (20 to 49 cm
subsidence) in the theoretical Tokai
Earthquake, or type-C or D failures
(Table 2). An overview of the soil
covering/nailing method is shown in
Figure 20.
• Viaduct unevenness and displacement
Response analysis of standard
Tokaido Shinkansen viaducts in
the theoretical Tokai Earthquake
shows the viaduct crown will sway
30 cm + 26 cm (amplification)
in response to ground sur face
movement of 30 cm if no earthquake
countermeasures are taken. However,
when countermeasures using X-shaped
damper braces (Figure
21) are taken, the swaying is 30 cm
+ 3 cm (amplification), reducing the
amplification displacement by 88.5%.
Misalignment must be controlled
be c au s e l o c a l i zed i r regu l a r
misalignment occurs easily due
to unevenness between adjacent
viaducts with over-hanging structures
(Figure 22). The target misalignment
is set to the acceptable horizontal
unevenness in an earthquake (3 cm)
based on railway displacement limit
design standards.
Horizontal displacement is about 3 cm
when using viaduct displacement countermeasures, and
horizontal unevenness is assumed to be about 6 cm when
adjacent viaducts respond out of phase. We confirmed
that displacement could be further reduced to about 2 cm
(approximately 30% of the assumption) using unevenness
countermeasures, meeting the requirement of about 3 cm.
Tsunami countermeasures
The catastrophic damage caused by the tsunami after
the Great East Japan Earthquake reconfirmed the need to
evacuate passengers safely and quickly rather than simply
strengthening facilities.
Following the devastating 2003 Sumatra Earthquake
tsunami, JR Central has been working with university
researchers on predicting damage from tsunami. The
tsunami height is simulated using a detailed 5-m mesh,
and locations at risk are defined taking into consideration
information from hazard maps (Figure 23) created by local
governments. Tsunami risk locations are being revised as
new hazard maps are released by local governments. In
December 2011, Mie Prefecture revised the tsunami risk
assuming a triple earthquake strike in the Tokai, Tonankai,
and Nankai areas. The 2003 assumptions of the Cabinet
Office Central Disaster Management Council for this type of
triple earthquake assumed no tsunami risk for the Tokaido
Shinkansen, putting only some parts of conventional lines at
risk. The December 2011 reassessment of tsunami risk led to
revised evacuation guidance and to tsunami evacuation drills
(Figures 24 and 25).
After the Great East Japan Earthquake, we simulated
tsunami flooding for a Magnitude 9.0 triple earthquake
in the Tokai, Tonankai, and Nankai areas (Figure 26).
Even with a tsunami of twice the height of the 2003
assumptions, nowhere on the Tokaido Shinkansen would
be flooded because the tracks are kilometers from the
coast and most civil-engineering structures such as
viaducts, bridges and embankments are 6 m or higher
above ground level.
Estimates of seismic intensity distribution and tsunami
height for a major earthquake in the Nankai Trough
(location of Magnitude 9.1 earthquake) were released by
the Cabinet Office Central Disaster Management Council
study group on 31 March 2012. Hazard maps are being
revised by local governments taking into account the
supposed flooding and we intend to revise the assumed
tsunami risk areas as necessary along with the required
actions for conventional lines.
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Figure 14: Overview of Derailment Prevention Guards
Figure 15: Effectiveness of Derailment Prevention Guards to Rocking Derailment
Figure 16: Full-Scale Test on Actual Bogie
Figure 17: Derailment Prevention Guards on Main-Line Tracks
Figure 18: Countermeasures to Ballast Flow Out
Figure 19: Countermeasures to Ballast Flow Out (Theoretical Tokai Earthquake)
Figure 20: Countermeasures to Embankment Subsidence (Soil Covering/Nailing)
Figure 21: Viaduct Displacement Countermeasures
Figure 22 Countermeasures to Viaduct Unevenness
Figure 23: Local Government Hazard Map (Mie Prefecture)
Figure 24: Efforts in Tsunami Evacuation
Figure 25: Tsunami Evacuation Drill
Figure 26: Cabinet Office Central Disaster Management Council Revised Tsunami Source Area
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Conclusion |
Disaster preparedness has been enhanced for civil engineering
structures but further countermeasures taking
into account aging and fatigue will probably be needed in the future.
Specific issues are weld fatigue on steel bridges,
neutralization of aged reinforced-concrete structures, and
effects of vibration and air pressure in tunnels. Since the
establishment of the Technology Research and Development
Department, we have been focusing on maintenance
and enhancement of civil-engineering structures as a key
issue. We have learned much in the past 10 years through
work on on-site situation analysis, full-scale model testing,
and analysis. A major issue for the future is how to perform
reasonable maintenance and enhancement at the best time.
We are also working to create a second route along
Japan’s key transport artery by constructing the Chuo
Shinkansen maglev. This will help assure continuity of
communications and transport in a disaster as well as help
support and maintain Japan’s economy.
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Further Reading
M. Seki, T. Matsuda, T. Arashika, Y. Sakamoto: Seismic Retrofit of Tokaido
Shinkansen Structures, J-Rail 2009, (December 2009)
M. Seki (edited by I. Nisugi): Tetsudo wo Kyodai Jishin kara Mamoru, pp
183-226, Sankaido Publishing, (November 2000)
T. Naganawa, M. Okano, A. Komatsu, H. Aikyo: A study on seismic
retrofitting system for RC column using divided steel plates, Journal of Japan
Society of Civil Engineers (Structural Engineering), Vol. 52A, pp 521-528,
(March 2006)
N. Kita, K. Yoshida, M. Okano, M. Seki: Practical Application of
Compression-type Steel Damping Braces for Railway Viaducts, Journal of
the JSCE, F, No.3, pp 277-286, (July 2007)
M. Seki, M. Ohki, T. Shoji, T. Nagao, T. Arashika: Experimental study on the
failure of the embankment and the effect of countermeasures on earthquake,
21st Symposium of the Chubu Branch of the Japanese Geotechnical Society,
(August 2009)
M. Hakuno, K. Meguro: Higai kara Manabu Jishin Kougaku, Kajima Institute
Publishing, (December 1992)
Ministry of Land, Infrastructure, Transport and Tourism Railway Bureau,
Railway Technical Research Institute: Design Standards For Railway
Structures and Commentary (Seismic Design), (October 1999)
T. Nagao, M. Seki, K. Sato: Ekijoka ni yoru Moritsuchi no Hakai Keitai
ni kansuru Kentou, 40th Japan National Conference on Geotechnical
Engineering, No.701, (July 2005)
T. Kachi, M. Seki, M. Kobayashi, T. Nagao, J. Koseki: Measures for
Preventing Derailment and Displacement on Tokaido Shinkansen Applied
Ballasted Track Reinforced with Geosynthetic Bags, J-Rail 2009, (December
2009)
K. Yoshida, T. Matsuda, H. Achiha, M. Seki: Derailment and dislodgement
prevention on Tokaido Shinkansen viaducts retrofitting with damping braces,
J-Rail 2009, (December 2009)
http://ci.nii.ac.jp/naid/110008010994
Ministry of Land, Infrastructure, Transport and Tourism Railway Bureau,
Railway Technical Research Institute: Design Standards For Railway
Structures and Commentary (Displacement Limits), (February 2006)
Mie Prefecture Department of Disaster Prevention: Tsunami no Shinsui
Yosoku (Fiscal 2011 version),
http://www.pref.mie.lg.jp/D1BOUSAI/tsunami/shinsuiyosokuzu.htm
Central Disaster Management Council: Nankai Trough no Kyodai Jishin
Model Kentoukai Chukan Torimatome (27 December 2011),
http://www.bousai.go.jp/jishin/chubou/nankai_trough/nankai_trough_top.html
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