Technology

Technology

Railway Technology Today 10 (Edited by Kanji Wako)

Minimizing the Effect of Natural Disasters
Tatsuo Noguchi and Toshishige Fujii
Geology and Weather—
Formidable Forces

Introduction

The earth’s crust is divided into more than
10 plates of different sizes. The plates risefrom submarine ridges, move laterally ata speed of 1 to 10 cm per year, then sink
into oceanic trenches. The Japanesearchipelago is located along several
plate boundaries. As Figure 1 shows, theJapanese islands are subjected totremendous stresses caused by thecollision of four massive plates.
The archipelago’s configuration wasdetermined by these forces. Violent
upthrusts throughout the entire island chain
during the Quaternary period, about 2
million years ago, produced topographicalfeatures with generally steep gradients, andgeological formations of faulted, weak rockthat extends far below the surface. Japanis still subject to great crustal stresses today
as the many active volcanoes and frequentJapan is situated in one of the most active
crustal zones in the world. The country’s
extremely diverse topography andgeology combine to create generally
unstable conditions, including frequent
earthquakes. The weather, too, can beunmerciful, bringing heavy rain and snow.
It is not surprising that a wide variety ofnatural disasters strike different parts ofJapan each year.
The nationwide rail network needs
protection from natural disasters. This
article looks at efforts taken by Japanese
railways, and research conducted by the
Railway Technical Research Institute(RTRI), to prevent damage caused byheavy rain and snow, gale-force winds,
major earthquakes and other natural
disasters.

Figure 1 Japan’s Proximity to Four Tectonic Plates and Plate Movement

Okhotsk
plate

Kuril
trenchJapan
trenchPacific
plate

Eurasian
plate

ugh

ai troNank

Ryukyutrench52

Philippine
sea plateJapan Railway & Transport Review 23 • March 2000

Izu-Ogasawara
trenchearthquakes indicate. As a result, Japan’s
geological makeup is quite different fromthat of many continental areas where strata
often date back to pre-Mesozoic times andthe land is relatively stable.
Rain and snowfall are heavy in Japanbecause it stretches from the monsoon
climate zone to the sub-arctic. Mean
annual precipitation (total rainfall andsnowfall) is about 1700 mm, or twice thatof much of Europe and the USA. And
because Japan’s landmass is elongatedand narrow, with steep mountain ranges,
there is a relatively high tendency—fourtimes greater than in Europe and theUSA—for rain and meltwater to wash
away the ground. Weathering and erosion
result in extensive surface degradation,
causing frequent landslides and otherdisastrous events.

Natural Disasters and Their
Impact on Railways
Figure 2 shows the number of times since
1966 that natural disasters (not including
earthquakes) have damaged railway tracks
in Japan. About 30 years ago, there wereabout 8000 incidents annually. But thisfigure has declined substantially sincethen, to stand at about 1000 incidents
now.
Figure 3 shows a breakdown of different
natural forces that have interrupted train
operations over the last 10 years. Flooddamage caused by typhoons andlocalized downpours occupies a
prominent position, followed by storm
and snow damage.
Steps to mitigate the effects of natural
disasters have helped reduce the numberof times railway operations have beeninterrupted, but natural forces still cause
derailments and accidents that kill andinjure passengers each year, so further
measures are required.

Copyright © 2000 EJRCF. All rights reserved.

Figure 2 Incidence of Damage to Japanese Railways by Natural Disasters

Figure 3 Different Natural
Forces Interrupting
Train Operations in
Last 10 Years

8,000
7,000

No. of disasters

6,000

Others

5,000

Flood
Rock fall
damageLightning
Averagedamage number of cases
peryear
Earthquake
damage
606

4,000
3,000
2,000

Snow damage
1,000

Storm damage

1966 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95

JNR

To limit the impact of natural disasters on
railway operations, we need to be able topredict time, location, and type. But weare dealing with natural phenomena thatare extremely hard to predict accurately,even with today’s advanced technology.
So Japanese railways have concentrated
their efforts on achieving safety anduninterrupted operations by combining
the following three types of measures:• Strengthening infrastructure
and installing protection devices
Railways try to mitigate the forces ofnature and prevent track damage in a
number of ways, particularly bystrengthening infrastructure. Tracks forshinkansen and other lines laid in therelatively recent past are generally
designed to withstand the forces of nature.
However, most conventional lines werebuilt decades ago and have many sections
that cannot withstand natural forces.

Copyright © 2000 EJRCF. All rights reserved.

Figure 4 Typical Train Operation Controls
80
Operation suspended
Speed regulated
Past records of disasters

70

60

Hourly rainfall r (mm/h)

Protective Measures

JR Companies

50

40

30

20

10

0
100

200

300

400

500

Accumulated rainfall R (mm)Japan Railway & Transport Review 23 • March 2000

53

Technology

These sections are being reinforced
gradually.
Typical measures, discussed later in moredetail, include slope protection, erectionof avalanche fences and wind barriers, andseismic reinforcement of infrastructure.
These measures are the most effective
possible but would be prohibitively
expensive if applied to every section of
every track, explaining why priority is given
to track sections that are at most risk ofnatural disasters.

• Train operation controls
When natural forces are strong enough toindicate the possibility of damage to trackor trains, trains are run at slower speeds
or operations are suspended. Indicesindicating accumulated rainfall (absolute
rainfall) and hourly rainfall (rainfall
intensity) are generally used to express
both of these factors in combination.
Figure 4 gives an example of train
operation controls applied to reduce therisks associated with rain. Rainfall
amounts and indices indicating reduced
speeds and interrupted service are shown.
Rising river indices are based on actual
water levels, wind indices are based on
instantaneous wind speed, and seismic
indices are based on the seismic motion
at ground level. The important question
regarding these train operation controls
remains; how to determine the values thatgovern operations? In actual practice,they are determined through experience,taking into account data from previous
disasters.

• Disaster detection
If natural forces create conditions that could
interfere with train operations, systems canquickly detect these conditions to stop thetrain and prevent damage. For example,
devices are installed to detect rock falls andavalanches, and the Urgent Earthquake
Detection and Alarm System (UrEDAS) has
been developed. Both are discussed below.
In some cases, one can detect signs that

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Japan Railway & Transport Review 23 • March 2000

Embankment collapse caused by heavy rain

warn of future trouble—for example, apartial land slippage or changes inunderground water level can indicate an
imminent landslide. We can use measuring
devices to predict and detect such an
occurrence. But the installation of suchdevices and measurements andobservations require significant manpowerand expense, so these devices are installed
only in a limited number of locations.

Safeguarding Trains from
Heavy Rainfall
Heavy rain can seriously disrupt rail
services. Rainwater can flood tracks,
wash away ballast and collapse slopes(e.g. embankment slopes, cut slopes, andnatural slopes). Flooding rivers can scour
bridge and revetment foundations. Rockfalls are another serious problem
encountered on slopes, although they
do not necessarily occur during heavy
rainstorms.
Various preventive structures are installed
along the track to prevent these problems(Fig. 5). Such structures are often the most

(RTRI)

effective, but, as previously mentioned,
they require huge expense. Anotherreason why they are not the answer toevery problem is that they are not disasterproof if the natural force is stronger thanthe design force. This means that we mustalso use train operation controls and,
where necessary, detection devices evenafter erection of protective structures.
Slope failure is the most common problem
associated with heavy rainfall, so measures
to prevent rain damage begin by preventing
slope failure. However, before deciding
which preventive measure would be mosteffective, we must first evaluate how muchrainfall will trigger a slope collapse.
Preventive structures and train operation
controls will be effective countermeasures
to heavy rainfall only if we can make sucha prediction with a high degree ofexactitude.
To increase prediction accuracy, RTRI
recently devised a new risk estimation
method for slope failure during heavy
rainfall. Risk estimations are made forthree types of slope failure: embankment
collapse, surface collapse on cuttings, andCopyright © 2000 EJRCF. All rights reserved.

deep collapse on cuttings. The estimatedslope failure risk value is expressed using
the term ‘critical rainfall’.
Figure 6, which indicates both hourly andaccumulated rainfall, plots sample results
obtained through this risk estimation
method. The critical rainfall curve
indicates withstanding force, with thehighest withstanding force in the upper
right of the figure. When the actual rainfall
is more than the values plotted on the
curve, the risk of collapse is great. Thisrisk estimation method has already been
adopted by the JR group of companies,
which are now using it to estimate slope
failure risks.
The extent to which a soil slope collapses
is closely related to the amount of rain,
but this is not necessarily the case withfalling rocks, which may fall even during
fine weather. Train operation controls are
therefore not very effective in preventing
damage caused by falling rocks.
Protective barriers and detection devices
are more effective. Such devices consistof cables laid near track areas where there
is a risk of falling rocks. When a cable issevered by a falling rock, an alarm isactivated and the train is stopped.

Figure 5 Major Structures to Prevent Damage by Landslides and Flooding

Rock catch fence

Cut slope protection
Rock catch wall

Copyright © 2000 EJRCF. All rights reserved.

Rock shed

Embankment slope
protection

Anti-scour protection

Figure 6 Critical Rainfall Curve
50
Area of probability ofslope failure occurrence40

Safeguarding Trains from
Heavy Snowfall

Deep collapse
Hourly rainfall r (mm/h)

Snow can seriously interfere with train
operations. Trains may be stopped by snow
accumulating on the tracks and turnouts,
or by drifting snow or avalanches.
Avalanches and snow drifts can derail a
train, snow can damage rolling stock, snow
adhering to rolling stock may fall off while
the train is in motion and cause an accident,
and railway structures may collapse under
the weight of snow.
A number of structures can be erected toprevent these and other problems (Fig. 7).
The snow can also be removed before it
becomes a serious nuisance using rotarysnowplows or Russel (pushing) snowplows.
In addition, winter schedules can be

Rock catch net

Restraining piles

30
Embankment collapse
Surface collapse
20

10

Safe area
Current operation
control threshold

0

100

200

300

400

Accumulated rainfall R (mm)Japan Railway & Transport Review 23 • March 2000

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Technology

Figure 7 Major Structures to Prevent Snow Damage

Cornice fence

Avalanche wedge

g

tin

all
ing w

Avalanche
breaking
structure

ec

che

n
Avala

efl

d
ppe
Ste race
tered

Avalanche
protection
forestdhenc
ala reAv uctu
str

nce

w fe
Sno

or t
upp s
ys
Gu ucture
str

nche
Avalance
fe

fence
Snow

retainSnow

shed
Snow fenceSnow melt

Snow run off ditch

Testing avalanche detection and alarm system at Shiozawa Snow Test Site. Pole in middle for avalanche detection(RTRI)

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Japan Railway & Transport Review 23 • March 2000

devised to permit the alternate use ofsnowplows and trains on the same track.
Tr a i n o p e r a t i o n c o n t r o l s c a n b e
implemented on a phased basis, dependingon the amount of snow on the tracks andsnow removal conditions.
Avalanche risk is evaluated from the air
using helicopters, and on the ground during
patrols. When an avalanche is anticipated,
especially during the snowmelt season,
special surveillance measures are taken toprotect rail operations. A different problem
is seen in tunnels—freezing of leaking
water. To prevent this, structures equippedwith thermal insulators are being developedand installed.
The following measures are taken toprotect shinkansen from snow damage. In
the case of the Tokaido Shinkansen line,
sprinklers spray water on ballasted track
during snowfalls. This makes snow wet,otherwise it would fly up when trains
speed by, and prevents snow fromadhering to rolling stock.
The Tohoku and Joetsu shinkansen lines run
through areas subject to greater snowfalls.
Ballasted track sections are shorter there,
and rolling stock is designed to inhibit snow
adherence. Viaducts on the Tohoku
Shinkansen line have been constructed towithstand snow depth equivalent to theannual return in a 10-year period. On the
Joetsu Shinkansen line, water sprinklers
melt snow on track sections in the plains
and on long, tunnel-free sections inmountainous areas. Snow sheds and snow
shelters have been constructed over shorter
sections between tunnels.

Interruption of rail services caused by heavy snow
(RTRI)

Copyright © 2000 EJRCF. All rights reserved.

Typical wind barrier

RTRI is now developing an avalanche
detection and alarm system for railway
tracks. We have completed basic research
on a system that will be extremely
accurate in detecting the occurrence ofavalanches and evaluating their size, andthat will issue alarms when required. Our
prototype experiments have indicated thatthe system can perform these functions
and we have every reason to believe that
it will be put to practical use soon.

Safeguarding Trains fromGale-force Winds
The greatest danger posed to a train by
gale-force winds is derailment. Wind issaid to have caused 29 derailments during
the more than 120 years of rail transportin Japan.
Other external forces also come into play,especially lateral inertia force andcentrifugal force. These external forces
can combine with gravitational force toexert a pressure that is directed toward
the leeward side of the wheels. Thispressure pushes the wheels away fromtheir point of contact with the rails,
causing the train to derail (Fig. 8).
One way to prevent this is to reduce
aerodynamic forces acting on rolling stock.
Another way is to measure wind speeds

Copyright © 2000 EJRCF. All rights reserved.

(JR Hokkaido)

Wind-tunnel test on aerodynamic forces of gale-force winds on rolling stock(RTRI)

Figure 8 External Forces on Rolling Stock and Critical Conditions for
Overturn (typical)

Storm

rce

Side force
ifting fo

L

Lateraliner tia

force

t
Momen
rce

ugal fo

Centrif

r force

Couplent ofResulta l forces
externa vityand graGravity

Japan Railway & Transport Review 23 • March 2000

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Technology

with trackside anemometers, and to stop
train operations on wind-prone track
sections when wind speeds indicate a needto do so. The first approach involves
installation of wind fences or windbreaks.
The second approach involves use of train
operation controls, which generally stop
services when the instantaneous windspeed reaches 30 m/s, or 25 m/s in areas
where even greater caution is warranted.
Once the train is halted, operation
guidelines call for it to stay halted for a full
30 minutes, and then to proceed only if
conditions indicate that wind speeds are
dropping.
RTRI is conducting wind-tunnel tests todetermine the extent to which various
rolling stock shapes, and the various
shapes of structures like bridges andembankments, can determine the intensityof wind-generated aerodynamic forces
against moving rolling stock. We are also
examining wind conditions along track
sections to discover the various
characteristics of wind. The results of thisresearch will be used to establish safe andeffective train operating control norms.

Safeguarding Trains from
Earthquakes
Japan is one of the most earthquake-prone
countries in the world. A recent example
is the Great Hanshin Earthquake thatstruck the Kobe region in January 1995,
causing considerable damage to railway
infrastructure, including the San’yo
Shinkansen line.
Measures to protect railways fromearthquakes include: (1) strengthening
infrastructure and equipment so that they
can withstand the anticipated earthquake
motion; and (2) stopping the train as soon
as an earthquake occurs, in order tominimize damage.
The second measure involves installationof trackside seismometers and theapplication of train operation controls.
The controls vary according to detected
seismic motion. Train operation controls
generally call for reduced speed when theearthquake acceleration is between 40
and 79 gals, and a rapid stop when theacceleration is 80 gals or greater. The
objective is to prevent the train fromentering a zone that has been damaged
by an earthquake. But the problem
remains that the train must travel somedistance while the ground is shaking

before coming to a complete halt. Thus,
this type of precaution may be inadequate,
especially in the case of a fast shinkansen.
To address this issue, RTRI developed theabove-mentioned Urgent Earthquake
Detection and Alarm System (UrEDAS),
which is designed to detect earthquake
forces more rapidly and transmit alarms
more accurately. As Figure 9 shows, thesystem detects an earthquake by picking
up small seismic waves called P-waves,which are the first to reach the Earth’s
surface. The system then immediately
estimates the epicenter and the magnitudeof the earthquake, and then uses this data
to determine risk levels. If the risk is great,
the system transmits alarms to areas that
could be affected. The object here is tohalt trains, or at least reduce their speed,
before the main shock arrives and causes
damage. When UrEDAS was first installed
in 1992, it covered the entire Tokaido
Shinkansen line. It has now been installedon all shinkansen tracks.
The other earthquake countermeasure—strengthening infrastructure andequipment—follows seismic design
standards established by the Japanese
government. Work has been carried out
to increase the earthquake resistance of
new structures and equipment, and of

Figure 9 Principle of Urgent Earthquake Detection
and Alarm System (UrEDAS)UrEDAS warning
P-wave arrival

Acceleration
warning
S-wave arrival

Initial tremor

Time
Main shock

Viaduct collapsed during Great Hanshin Earthquake

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Japan Railway & Transport Review 23 • March 2000

(RTRI)

Copyright © 2000 EJRCF. All rights reserved.

Seismometer (left) installed at UrEDAS site (middle) and data processing unit at Seismic Data & Analysis Center

existing structures and equipment in areas
where it is thought a major earthquake
could strike.
However, the motion of the 1995
earthquake in the Kobe area greatly
exceeded any earthquake movement
expected at the time. Therefore, RTRI
revised its seismic design principles. Twonotable results of this revision are: (1) inthe past, any study of extremely strong
earthquake motion focused on interplate
earthquakes, but consideration is now also
given to earthquakes along inland active
faults; and (2) structural design is based on
the principle that structures must notcollapse during an earthquake even though
they may sustain damage. Decisions
regarding structural seismic capacity arebased on each structure’s importance.

(Photos: RTRI)

also been used recently.
Effective train operation controls requirecontinuous and accurate assessment ofmeteorological conditions. Over the years,
this has meant trackside installation of rain
gauges, anemometers and other devices.
In some cases, such devices can now beaccessed online, making it possible tocollect data in real time. Greater precision
is also achieved using data from Japan’sMeteorological Agency. We must also
increase the reliability of technologies used
to predict natural disasters, and develop
other effective and economical means tosafeguard railways from the forces of nature.
RTRI is conducting serious research to
tackle these issues.
■

Conclusion
It is impossible to prevent an act of God
from inflicting damage on railway
infrastructure, but appropriate measures
can make infrastructure less vulnerable.
First, for any protective measure to beeffective, railways must always remainaware of conditions on and near theirtracks, and must take appropriate steps
whenever there is a risk of disaster.
Japanese railway companies inspect theirtracks and equipment on a regular basis,
and information obtained from these
inspections is used when devisingprotective measures. Inspections are
conducted mainly by engineers, but newtechniques, such as remote sensing, have

Kanji Wako
Mr Kanji Wako is Director in Charge of Research and Development at the Railway Technical Research Institute (RTRI). He joined JNR in 1961 after graduating in engineering from Tohoku
University. He is the supervising editor for this series on Railway Technology Today.

Tatsuo Noguchi

Toshishige Fujii

Mr Noguchi joined JNR in 1973 after graduating in geology fromMr Fujii joined JNR in 1974 after completing a postgraduate science

Tohoku University. He left the Structure Maintenance Section of JNR

course at Hokkaido University. He held a variety of posts in the Track

Head Office in 1987 to join the newly formed Railway Technical& Structure Department before becoming Chief Researcher in the

Research Institute (RTRI) where he is now General Manager of the

Geotechnical Engineering Laboratory of RTRI in 1987. He is currently

Environmental Preservation & Disaster Prevention Technology

Chief Research Engineer in the Meteorological Disaster Prevention

Development Division.

Group.

Copyright © 2000 EJRCF. All rights reserved.

Japan Railway & Transport Review 23 • March 2000

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