Tuneles Sismo Japon

7/27/2019 Tuneles Sismo Japon

1/6

136136136136136 QR of RTRI, Vol. 48, No. 3, Aug. 2007

PAPERPAPERPAPERPAPERPAPER

Historical Earthquake Damage to THistorical Earthquake Damage to THistorical Earthquake Damage to THistorical Earthquake Damage to THistorical Earthquake Damage to Tunnels in Japan and Case Studiesunnels in Japan and Case Studiesunnels in Japan and Case Studiesunnels in Japan and Case Studiesunnels in Japan and Case Studies

of Railway Tof Railway Tof Railway Tof Railway Tof Railway Tunnels in the 2004 Niigataken-Chuetsu Earthquakeunnels in the 2004 Niigataken-Chuetsu Earthquakeunnels in the 2004 Niigataken-Chuetsu Earthquakeunnels in the 2004 Niigataken-Chuetsu Earthquakeunnels in the 2004 Niigataken-Chuetsu Earthquake

1. Introduction1. Introduction1. Introduction1. Introduction1. Introduction

Since mountain tunnels are generally surrounded by

stable ground, their displacement during seismic activ-

ity tends to be minimized, making them less susceptible

to seismic damage than other structures such as bridges

and foundations (Fig. 1). However, earthquake-resistant

tunnels have been highly noted since the 2004 Niigataken-Chuetsu Earthquake. Some tunnels in the disaster area

were heavily damaged by the quake, and represented

obstacles to the reopening of Shinkansen and conventional

lines. In particular, the concrete lining of the Jyoetsu

Shinkansens Uonuma Tunnel (located adjacent to the

epicenter) was heavily damaged, requiring a two-month

period for restoration.

Advances in construction technology mean that more

and more railway structures are built using the tunnel-

ing method, and tunnels too need a sufficient level of

earthquake resistance. In this paper, we introduce case

studies on historical damage to mountain tunnels, an

outline of the damage and its assumed causes resulting

from the above earthquake 1).

2. Historical damage to mountain tunnels caused by2. Historical damage to mountain tunnels caused by2. Historical damage to mountain tunnels caused by2. Historical damage to mountain tunnels caused by2. Historical damage to mountain tunnels caused by

earthquakesearthquakesearthquakesearthquakesearthquakes

2.1 Outline of damage2.1 Outline of damage2.1 Outline of damage2.1 Outline of damage2.1 Outline of damage

Figure 2 summarizes the large-scale earthquakes that

damaged mountain tunnels on railways in Japan. There

have been four major earthquakes: the 1923 Kanto Earth-

quake, the 1978 Izu-Oshima-Kinkai Earthquake, the 1995

Hyogoken-Nanbu Earthquake and the 2004 Niigataken-

Chuetsu Earthquake. An outline of the damage to moun-

tain tunnels in each earthquake is given below.

Kazuhide YKazuhide YKazuhide YKazuhide YKazuhide YASHIROASHIROASHIROASHIROASHIRO

Assistant Senior Researcher,

YYYYYoshiyuki KOJIMA, Droshiyuki KOJIMA, Droshiyuki KOJIMA, Droshiyuki KOJIMA, Droshiyuki KOJIMA, Dr.Eng..Eng..Eng..Eng..Eng.

Senior Researcher, Laboratory Head,Tunnel Engineering Laboratory, Structures Technology Division

Mitsuru SHIMIZUMitsuru SHIMIZUMitsuru SHIMIZUMitsuru SHIMIZUMitsuru SHIMIZU

Manager,

Structural Engineering Center, East Japan Railway Company

Since mountain tunnels are generally surrounded by stable ground, their displace-

ment during seismic activity tends to be minimized, making such structures less suscep-

tible to seismic damage. Despite this, many railway mountain tunnels have sustained

damage, from the 1923 Kanto Earthquake to the 2004 Niigataken-Chuetsu Earthquake.

This paper provides an outline of the historical damage to mountain tunnels in Japan

and outlines the results of case studies on damage sustained in mountain tunnels. Also

outlined here is a classification of the damage patterns and the conditions of damage

based on the results of the case studies, and we refer to the estimated causes of damage totunnels in the 2004 Niigataken-Chuetsu-Earthquake.

KeywordsKeywordsKeywordsKeywordsKeywords: mountain tunnel, earthquake, case studies

Fig. 1 Behavioral difFig. 1 Behavioral difFig. 1 Behavioral difFig. 1 Behavioral difFig. 1 Behavioral differences during an earthquakeferences during an earthquakeferences during an earthquakeferences during an earthquakeferences during an earthquake

between bridges, foundations and mountainbetween bridges, foundations and mountainbetween bridges, foundations and mountainbetween bridges, foundations and mountainbetween bridges, foundations and mountain

tunnelstunnelstunnelstunnelstunnels

Fig. 2 Historical damage to mountain tunnels caused byFig. 2 Historical damage to mountain tunnels caused byFig. 2 Historical damage to mountain tunnels caused byFig. 2 Historical damage to mountain tunnels caused byFig. 2 Historical damage to mountain tunnels caused byearthquakes in Japanearthquakes in Japanearthquakes in Japanearthquakes in Japanearthquakes in Japan

Mountain tunnel

Hard ground

Soft ground

Bridge and foundation

DisplacementLarge

Earthquake

Soft ground DamageLarge

Inertia forceLarge

Earthquake

DisplacementSmall

DamageSmall

Inertia forceSmall

7

7

5

67.9

-tudeYear, Name

Damage to 24 tunnels5 tunnels required reinforcement

6.82004Niigataken-Chuetsu


7.21995Hyogoken-Nanbu


7.01978Izu-Oshima-Kinkai


1923Kanto

Tunnel performanceSeismicintensity

Magni


2/6

137137137137137QR of RTRI, Vol. 48, No. 3, Aug. 2007

2.2 The 1923 Kanto Earthquake2.2 The 1923 Kanto Earthquake2.2 The 1923 Kanto Earthquake2.2 The 1923 Kanto Earthquake2.2 The 1923 Kanto Earthquake

The 1923 Kanto Earthquake caused the maximum

damage ever recorded in modern Japanese history, and

also caused the most damage to mountain tunnels. 149

railway tunnels were located within a 120-km radius of

the epicenter at the time. 93 of them sustained damaged

requiring reinforcement, while 25 required complete re-

construction. The earthquake resulted in many tunnels

being buried underground, and linings were destroyed by

ground collapses.

2.3 The 1978 Izu-Oshima-Kinkai Earthquake2.3 The 1978 Izu-Oshima-Kinkai Earthquake2.3 The 1978 Izu-Oshima-Kinkai Earthquake2.3 The 1978 Izu-Oshima-Kinkai Earthquake2.3 The 1978 Izu-Oshima-Kinkai Earthquake

Nine railway tunnels sustained damage in the 1978

Izu-Oshima-Kinkai Earthquake. The greatest damage

occurred in the Inatori Tunnel, where a fault crossing

the tunnel slid during the earthquake, causing a collapse

of the tunnel lining and longitudinal displacement of thetrack. The relative displacement of the fault was 70 cm

horizontally and 20 cm vertically according to survey re-

sults.

2.4 The 1995 Hyogoken-Nanbu Earthquake2.4 The 1995 Hyogoken-Nanbu Earthquake2.4 The 1995 Hyogoken-Nanbu Earthquake2.4 The 1995 Hyogoken-Nanbu Earthquake2.4 The 1995 Hyogoken-Nanbu Earthquake

The 1995 Hyogoken-Nanbu Earthquake caused the

most damage of all Japanese earthquakes in recent times.

In this earthquake, seven of the 43 railway mountain

tunnels located within the disaster area sustained seri-

ous damage, and five tunnels required repair and rein-

forcement. A typical example was the Rokko Tunnel,

which sustained compressive damage, shear failure at the

arch of the lining and compressive failure with spalling

at the joints between the arch and the sidewall, and took

three months to reopen.

2.5 The 2004 Niigataken-Chuetsu Earthquake2.5 The 2004 Niigataken-Chuetsu Earthquake2.5 The 2004 Niigataken-Chuetsu Earthquake2.5 The 2004 Niigataken-Chuetsu Earthquake2.5 The 2004 Niigataken-Chuetsu Earthquake

On October 23 2004, a large earthquake of 6.8 in

magnitude occurred at latitude 3717 N. and longitude

13852 E. at a depth of 13 km in Japans Niigata Prefec-

ture. The earthquake caused a running Shinkansen trainto derail, and some mountain tunnels sustained severe

damage. 24 railway tunnels were seriously damaged,

and five (the Uonuma, Myoken, Wanatsu, Tenno and

Shin-Enokitoge tunnels) required lining repair and re-

inforcement. Table 1 shows a list of the damaged rail-

way tunnels, Fig. 3 shows the distribution of heavily

damaged railway tunnels and Fig. 4 shows the number

of damaged tunnels. It is clear that the heavily dam-

TTTTTable 1able 1able 1able 1able 1 List of the damaged railway tunnelsList of the damaged railway tunnelsList of the damaged railway tunnelsList of the damaged railway tunnelsList of the damaged railway tunnels

Fig. 3 Distribution of railway tunnels heavily damaged inFig. 3 Distribution of railway tunnels heavily damaged inFig. 3 Distribution of railway tunnels heavily damaged inFig. 3 Distribution of railway tunnels heavily damaged inFig. 3 Distribution of railway tunnels heavily damaged in

the Niigataken-Chuetsu Earthquakethe Niigataken-Chuetsu Earthquakethe Niigataken-Chuetsu Earthquakethe Niigataken-Chuetsu Earthquakethe Niigataken-Chuetsu Earthquake Fig. 4 Number of damaged tunnelsFig. 4 Number of damaged tunnelsFig. 4 Number of damaged tunnelsFig. 4 Number of damaged tunnelsFig. 4 Number of damaged tunnels

Jyo

-e

tsu

Shink

ansen

Iiyam

aLine

Jyo-etsu

Lin

e

Niigata

Miyauchi St.

10km

20km

Shi

n-etsu

Line

Tad

amiL

ine

Epicenter Magnitude 6.8

Myoken T.

Wanatsu T.

Uonuma T.Tenno T.

Shin-Enokitoge T.

N

Uonuma T. Name of heavily damaged tunnel

Tokyo

Nagaoka St.

Urasa St.

Degree of damage

Number

ofdamaged

tunnels

Degree of damage:

A1: Heavy damage requiring repair and reinforcement

A2: Damage requiring repair and reinforcement

B: Damage not requiring repair and reinforcement

C: No damage

Tunnel

Line

Degree

of

damage

Damage

Days

required

for restoration

Jyoetsu

Shinkansen

Uonuma A1 Detached lining, cracks, heaving 66

Myoken A1 Compressive failure, cracks, heaving 66

Jyoetsu

conventional

line

Wanatsu A1 Detached lining, compressive failure, cracks 65

Tenno A1 Cracks 65

Shin-Enokitoge A1 Compressive failure, cracks 65

Note:

Degree of damage

A1Heavy damage requiring repair and reinforcement


3/6


aged tunnels are concentrated in a limited area approxi-

mately within a 10-km radius from the epicenter. The

most heavily damaged was the Uonuma Tunnel, which

runs nearby the epicenter. The Uonuma Tunnel is an

8,625-m long railway tunnel running through Neogene

mudstone. Three sections of the tunnel sustained heavy

damage (Fig. 5).Figure 6 shows the damage in the most heavily af-

fected section. The concrete lining broke and fell onto the

track. The largest concrete block was approximately 2m3

with a weight of five tons. Other damage observed con-

sisted of a reduction in the tunnel diameter, heaving of

the roadbed concrete and invert cracking. This was the

biggest disaster of all Shinkansen tunnels since the in-

troduction of the system. Figure 7 shows the reinforce-

ments made to the Uonuma Tunnel. The locations were

restored through rock bolting, concrete removal using

breakers, shotcreting and reinforcement using precast

Fig. 5 Longitudinal profile and damage locations in theFig. 5 Longitudinal profile and damage locations in theFig. 5 Longitudinal profile and damage locations in theFig. 5 Longitudinal profile and damage locations in theFig. 5 Longitudinal profile and damage locations in theUonuma TUonuma TUonuma TUonuma TUonuma Tunnelunnelunnelunnelunnel

Northportal

194km 196km 198km 200km

(m)

200

100

Southportal

UonumaTunnel

20m90m 100m

Heavily damaged section

Neogene's mudstone For NiigataFor Tokyo

Fig. 6 Damage to the Uonuma TFig. 6 Damage to the Uonuma TFig. 6 Damage to the Uonuma TFig. 6 Damage to the Uonuma TFig. 6 Damage to the Uonuma Tunnelunnelunnelunnelunnel

Liningdetachment

Fig. 7 Repairs to the Uonuma TFig. 7 Repairs to the Uonuma TFig. 7 Repairs to the Uonuma TFig. 7 Repairs to the Uonuma TFig. 7 Repairs to the Uonuma Tunnelunnelunnelunnelunnel

Fig. 8 Damage to the Myoken TFig. 8 Damage to the Myoken TFig. 8 Damage to the Myoken TFig. 8 Damage to the Myoken TFig. 8 Damage to the Myoken Tunnelunnelunnelunnelunnel

Fig. 9 Repairs to the Myoken TFig. 9 Repairs to the Myoken TFig. 9 Repairs to the Myoken TFig. 9 Repairs to the Myoken TFig. 9 Repairs to the Myoken Tunnelunnelunnelunnelunnel

Fig. 10 Damage to the WFig. 10 Damage to the WFig. 10 Damage to the WFig. 10 Damage to the WFig. 10 Damage to the Wanatsu Tanatsu Tanatsu Tanatsu Tanatsu Tunnelunnelunnelunnelunnel

Rock boltL=3m

Shotcrete

Fiber-reinforcedprecast boardt=50mm

Crack repair(Grout)

Joint repair(Cast-in place

concrete)

Compressive failure

Spalling

Compressivefailure

mortar boards, but the tunnel was a critical path and took

two months to reopen.

Further damage occurred in the Jyoetsu

Shinkansens Myoken Tunnel, which sustained compres-

sive failure at the crown with a longitudinal length of

approximately 50 m (Fig. 8), and an invert heaved as in

the case of the Uonuma Tunnel. Figure 9 shows the re-inforcements made to the Myoken Tunnel. The locations

were restored through rock bolting, concrete removal

Liningdetachment

Shotcrete

Fiber-reinforcedprecast boardt=50mm

Crack repair(Grout)

Joint repair(Cast-in-place

concrete)

Rock bolt

L=3m


4/6


using breakers, shotcreting and fiber-reinforced boards.

The conventional-line Wanatsu Tunnel sustained

compressive failure at the crown with a longitudinal

length of about 40 m, and large blocks fell off the lining

exposing the steel supports of the tunnel (Fig. 10).

In the Tenno and Shin-Enoki tunnels, the bedrock

above the tunnel collapsed and slid, cracks occurred inthe lining, and the tunnel portal was buried by earth

and sand. However, this damage was caused indirectly

by the collapse of the ground/slope, and the earthquake

did not result in any direct damage to the tunnels.

3. Classification of damage patterns3. Classification of damage patterns3. Classification of damage patterns3. Classification of damage patterns3. Classification of damage patterns

Figure 11 shows the results of classifying the dam-

age patterns in the 1978 Izu-Oshima-Kinkai Earthquake,

the 1995 Hyogoken-Nanbu Earthquake and the 2004

Niigataken-Chuetsu Earthquake, for which a range of

valuable information and data is available. The dam-

age patterns have also been classified into three typesas shown in Fig. 12.

Type 1: Damage to shallow tunnels (Fig. 13)

There are many examples of tunnel damage in the

Type 1 category. In general, shallow tunnels are likely to

be affected by earthquakes as they are often constructed

in loose ground, where seismic activity amplifies and

causes large ground deformation. Cracks in the arch of

the lining are characteristic of this type. It is conceiv-

able that tunnels deform by shearing as a result of dis-

placement caused by the earthquake and cracks occur at

the shoulder part of arches due to bending moments.

Type 2: Damage to tunnels in poor geological conditions

(Fig. 14)

This type of damage is visible in tunnels in soft ground

such as fractured zones, sometimes in tunnels with a large

earth covering. In fractured zones, the ground is gener-

ally soft, resulting in large displacement in earthquakes.

Other loads also act on the lining, such as loosening earth

pressure and plastic earth pressure in the fractured zone

before an earthquake. In such cases, the load acting on

the lining increases, and damage caused by earthquakes

tends to be severe.

Type 3: Damage to tunnels by fault slide (Fig. 15)

Type-3 damage occurs when an earthquake faultcrosses a tunnel. Various stresses result from earthquake

fault sliding (such as shear stress, tensile stress and com-

pressive stress on the lining) and cause complicated cracks

including shear cracks and cracks in round slices.

Many of the damaged tunnels are classified into these

three types of damage pattern as shown in Fig. 11.

4. Conditions of damage4. Conditions of damage4. Conditions of damage4. Conditions of damage4. Conditions of damage

From such case studies, it is evident that even moun-

tain tunnels sustain earthquake-related damage. Theconditions under which tunnels are susceptible to dam-

Fig. 1Fig. 1Fig. 1Fig. 1Fig. 11 Number of damaged tunnels (by damage type)1 Number of damaged tunnels (by damage type)1 Number of damaged tunnels (by damage type)1 Number of damaged tunnels (by damage type)1 Number of damaged tunnels (by damage type)

Fig. 12 Classification of damage patternsFig. 12 Classification of damage patternsFig. 12 Classification of damage patternsFig. 12 Classification of damage patternsFig. 12 Classification of damage patterns

Fig. 13 Damage to shallow tunnelsFig. 13 Damage to shallow tunnelsFig. 13 Damage to shallow tunnelsFig. 13 Damage to shallow tunnelsFig. 13 Damage to shallow tunnels

Fig. 14 Damage to tunnels in poor geological conditionsFig. 14 Damage to tunnels in poor geological conditionsFig. 14 Damage to tunnels in poor geological conditionsFig. 14 Damage to tunnels in poor geological conditionsFig. 14 Damage to tunnels in poor geological conditions

Fig. 15 Damage to tunnels caused by fault slideFig. 15 Damage to tunnels caused by fault slideFig. 15 Damage to tunnels caused by fault slideFig. 15 Damage to tunnels caused by fault slideFig. 15 Damage to tunnels caused by fault slide

0

1

2

3

4

5

Type1 Type2 Type3 The others

Numbe

rofheavily

damagedtunnels

II. Poor geological

conditions

III. Faultslide

I. Shallow tunnel

Frac

ture

zon

e

Fault

EarthquakeHard ground

Softground

Bending crackI. Shallow tunnel

Displacementcaused by earthquake

Earthquake

Additional loadcaused by earthquake

Fracture zone

Load actingbefore earthquake

Spalling

Shear crack

II. Poor geological conditions

Complicated cracks

Fault surface

Slide

Slide

Gap

III. Fault slide


5/6


age are:

(1) Earthquakes of great magnitude

(2) Tunnel location adjacent to an epicenter or an earth-

quake fault

Figure 16 shows the relationship between the dis-

tance from the earthquake fault, the magnitude of the

earthquake and the number of heavily damaged tunnels.From this figure, we find that the risk of earthquake

damage becomes large under both conditions (1) and (2)

outlined above. Roughly speaking, tunnels sustained

considerable damage in areas within 10 km of an earth-

quake fault in the case of M7, and areas within 30 km in

the case of M8. Figure 17 shows the relationship be-

tween the distance from an earthquake fault and the

percentage of tunnels damaged. From this figure, we

find that damage requiring reinforcement occurred

within 10 km of an earthquake fault.

However, these figures do not fully consider the con-

ditions specific to tunnels such as the ground adjacent

to the tunnel and the tunnel structure. It is conceivable

that tunnels tend to be vulnerable to earthquakes under

certain circumstances, such as:

0 10 20 306.8

7.0

7.2

7.4

7.6

7.8

8.0

Magnitude(M)

Distance from earthquake fault (km)

421

1

1

1

16 1923 Kanto

1930 Kita-Izu

1995 Hyogoken-nanbu1948 Fukui

1978 Izu-

Oshima-Kinkai

2004 Niigataken-

Chuetsu

Bound

ary

line

causin

gheavy

damag

e

1 Tunnels requiringreinforcement(needing several daysto reopen)

2

2 2

3 2

5

40

Hyogoken-Nanbu

Distance from earthquake fault (km)

0

20

40

60

80

100

Percentage(%)

0-5

5-10

10-15

15-

0

20

40

60

80

100

0-5

5-10

10-15

15-

Percentage(%)

Niigataken-Chuetsu

Heavily damaged tunnels

Fig. 17 Relationship between the distance from theFig. 17 Relationship between the distance from theFig. 17 Relationship between the distance from theFig. 17 Relationship between the distance from theFig. 17 Relationship between the distance from the

earthquake fault and the percentage of heavilyearthquake fault and the percentage of heavilyearthquake fault and the percentage of heavilyearthquake fault and the percentage of heavilyearthquake fault and the percentage of heavilydamaged tunnelsdamaged tunnelsdamaged tunnelsdamaged tunnelsdamaged tunnels

Fig. 16 Relationship between the distance from anFig. 16 Relationship between the distance from anFig. 16 Relationship between the distance from anFig. 16 Relationship between the distance from anFig. 16 Relationship between the distance from an

ear thquake fau l t , the magni tude of theear thquake fau l t , the magni tude of theear thquake fau l t , the magni tude of theear thquake fau l t , the magni tude of theear thquake fau l t , the magni tude of the

earthquake and the number of heavily damagedearthquake and the number of heavily damagedearthquake and the number of heavily damagedearthquake and the number of heavily damagedearthquake and the number of heavily damaged

tunnelstunnelstunnelstunnelstunnels

a. shallow tunnels

b. poor geological conditions

c. sliding of an earthquake fault crossing the tunnel

d. structural defects in the tunnel lining

Figure 18 shows the number of damaged tunnels inwhich these circumstances are found. Many of the heavily

damaged tunnels feature some of these special conditions.

It can therefore be concluded that the risk of earthquake

damage becomes large under the conditions of both (1)

and (2), and that the level of damage becomes large when

there is at least one special condition.

5. Causes of damage to the Uonuma T5. Causes of damage to the Uonuma T5. Causes of damage to the Uonuma T5. Causes of damage to the Uonuma T5. Causes of damage to the Uonuma Tunnelunnelunnelunnelunnel

In this chapter, we introduce the causes of damage to

the Uonuma Tunnel, which sustained the heaviest dam-

age in the 2004 Niigataken-Chuetsu Earthquake.Firstly, this tunnel was within 1 km of the epicen-

ter, and the earthquake motion was extremely strong.

Secondly, the ground in this area is Neogene mudstone

and is relatively soft. We surveyed the geological char-

acteristics and the situation behind the tunnel lining by

boring in the most heavily damaged section, and two

conclusions were reached. Firstly, the ground in the dam-

aged section had a lower strength than that in neighbor-

ing sections (Fig. 19). Secondly there were voids behind

the tunnel lining at the arch, and the tunnel was subject

to large deformation.

It is conceivable that the Uonuma Tunnel sustained

large damage due to its location adjacent to the epicen-

Fig. 18 Number of damaged tunnels featuring the specialFig. 18 Number of damaged tunnels featuring the specialFig. 18 Number of damaged tunnels featuring the specialFig. 18 Number of damaged tunnels featuring the specialFig. 18 Number of damaged tunnels featuring the special

conditions (in the Kanto Earthquake and the Izu-conditions (in the Kanto Earthquake and the Izu-conditions (in the Kanto Earthquake and the Izu-conditions (in the Kanto Earthquake and the Izu-conditions (in the Kanto Earthquake and the Izu-

Oshima-Kinkai Earthquake)Oshima-Kinkai Earthquake)Oshima-Kinkai Earthquake)Oshima-Kinkai Earthquake)Oshima-Kinkai Earthquake)

0

10

20

30

40

50

60

70

Large Medium SmallNumberof

damagedtunnels

Without special conditions

With special conditions

Damage Level

Fig. 19 Geological characteristics in the damaged sectionFig. 19 Geological characteristics in the damaged sectionFig. 19 Geological characteristics in the damaged sectionFig. 19 Geological characteristics in the damaged sectionFig. 19 Geological characteristics in the damaged sectionof the Uonuma Tof the Uonuma Tof the Uonuma Tof the Uonuma Tof the Uonuma Tunnel (ground plan)unnel (ground plan)unnel (ground plan)unnel (ground plan)unnel (ground plan)

TuffSandstone

Alternation of strata(Mudstone and sandstone)

Tokyo Niigata

Rightsidewall

Leftsidewall

Damaged section

Fractured zone10m0m

Mudstone


6/6


ter, the extremely strong earthquake motion and the pres-

ence of voids behind the tunnel lining.

6. Countermeasures against earthquakes for tunnels6. Countermeasures against earthquakes for tunnels6. Countermeasures against earthquakes for tunnels6. Countermeasures against earthquakes for tunnels6. Countermeasures against earthquakes for tunnels

We are currently planning countermeasures againstearthquake damage. Figure 20 shows the methods used

in existing tunnels. Backfill-grouting of voids behind lin-

ings and rock bolting to prevent spalling are among the

fundamental countermeasures. For newly constructed

tunnels, the countermeasures are adapted in the linings

themselves. We use fiber-reinforced concrete to improve

the ductility and performance of lining anti-spalling.

Fig. 20 Fundamental countermeasuresFig. 20 Fundamental countermeasuresFig. 20 Fundamental countermeasuresFig. 20 Fundamental countermeasuresFig. 20 Fundamental countermeasures

Backfill grouting Rock bolt

7. Conclusions7. Conclusions7. Conclusions7. Conclusions7. Conclusions

This paper gives an outline of the historical damage

to mountain tunnels in Japan and resultant case studies

of damage found in mountain tunnels. We also show a

classification of damage patterns and the conditions of

damage based on the case study results. However, manyfactors relating to the damage mechanism of tunnels in

an earthquake remain unknown. It is essential to estab-

lish a method of evaluating the earthquake resistance of

tunnels. We are currently planning model tests and nu-

merical analysis to evaluate the deformation behavior of

tunnels under earthquake conditions, and plan to use the

results in the maintenance of railway tunnels.

ReferencesReferencesReferencesReferencesReferences

1) Shimizu, M., Suzuki, T., Kato, S., Kojima, Y., Yashiro,

K. and Asakura, T.: Historical Damages of Tunnels

in Japan and Case Studies of Damaged Railway Tun-nels in the Mid Niigata Prefecture Earthquakes, ITA-

AITES World Tunnel Congress 2007, Prague, Czech

Rep., May 2007.

Documents

Tuneles Sismo Japon