Failure Knowledge Database / 100 Selected Cases

Fire in Oshimizu tunnel【20th March 1979, Minakami Town, Tone District, Gunma Prefecture】
Masayoshi

Kitajima(MaedaConstruction

Company,Headquarter

of

Safe

Environment, Safe Environment Bureau, Safe Labor Group, Fulltime Chief Director)
On 20th March 1979, in Minakami Town, Tone District, Gunma Prefecture, a fire
broke out from the Hotonozawa construction field (5350m-long) in Oshimizu tunnel(22.3km-long as a whole) when Maeda Corp doing demolition of the steel jumbo drill
stand. As a result, 14 out of 54 workers and 2 workers, who went into the tunnel withthe self-contained compressed air breathing apparatus to figure out the condition,
were surrounded by the smoke and died of the carbon monoxide intoxication.

Map of Oshimizu tunnel

Smoke from the entrance of Hotonozawa mine (photograph: Kyodo News Service)1

Failure Knowledge Database / 100 Selected Cases

1. Event
Oshimizu tunnel was divided into 6 construction sections, Hotonozawa construction
section, in which fire broke out, was the second section from Omiya. An inclined shaft(518m) was established for the boundary between the first section and this section,and, in this section, 5350m-long tunnel was supposed to be constructed to the Niigata
prefectural boundary.
On that day, 11 persons, consisted of 1 staff and 10 workers, were in charge of thedemolition of the jumbo drill stand (two stage of decks, upper stage and middle stage),and they started working from around 20 o'clock. At around 21:30, they were doing
fusion cuttings of the volt of boom mount on the upper deck of the jumbo drill by theoxyacetylene gas fusion cutting machine, then sparks of fusion cutting, etc. fell onto
the middle deck and set fire to the oily wood chips which were piled up and adhered tothe deck. After the flame was found, they tried to extinguish fire by the three fire
extinguisher equipped with on the jumbo drill. However they all failed to emit thepowder in the fire extinguisher, besides the wind from Niigata because of thepenetration of tunnel helped the fire to broaden. Finally they gave up fire
extinguishing, and escape and report to another workplace were conducted.

21 boom-jumbo drill stand(Source: Author made)8 out of 11 workers in the group of demolition of jumbo drill stand succeeded toescape, since they ran to Niigata. But 3 workers who moved toward Omiya failed toescape and died winding by the smoke; this direction was windward. Also, although 3
out of 14 workers, who were doing lining concrete installation work (this work is;assembling the tunnel-shape mould, and pouring the concrete there) in the field which2Failure Knowledge Database / 100 Selected Cases

was 254m-windward from the fire, succeeded in the escape to Omiya, 11 workers
failed to escape and died winding by smoke. All the other workers who worked on theway managed to escape.
In the meantime, the two staff who received the report in the office went into mineto grasp the situation from the inclined shaft, with the self-contained compressed air
breathing apparatus (Baitasu). But they also died winding by smoke, on the way tothe office.

Cross-section figure of Oshimizu tunnel
２.

(Source: Author made)CourseCeremony for the penetration of the whole lines of Oshimizu tunnel was done on
January 25th 1979, after that, aiming to complete construction in September, thelining concrete and etc. were preceded. The jumbo drill stand became unnecessary anddemolition work started from the day before the accident day (19th March), since thefull cross section off spread excavation finished about 20 days after the ceremony.
Night duty work on 20th of Marches in the accident day was carried out by 2 staff
and 52 workers. The demolition work had been carried out by 1 staff and 10 workers
at the place where it was about 70m close to Omiya from the Niigata-side boundary of
the construction section. The lining concrete installation, where the largest number ofworkers suffered from the fire, was conducted by 1 staff and 13 workers at the placeabout 254m close to Omiya from the demolition workplace.

In addition, there weresuch operations done in the tunnel as the secondary lining concrete installation work(16 workers), the mould assembly of the center sewage (6 workers), the preparatory

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Failure Knowledge Database / 100 Selected Cases

work of “Ryoban” concrete installation (4 workers), and the waste water treatment
work (3 workers).
The fire broke out around 21:30, and the first report was sent to the office around21:40 from the staff in charge of the lining concrete work group. The report said thatfire had broken out and they did fire extinguishing. There was no report after the firstreport.
３．Cause(1)

Combustibles were scattered around the fire service space.

On the deck of the jumbo drill stand, wood chips etc. generated when cutting off thewood for the tunnel support piled up and adhered. In addition, they were easy to beburned because they sponged the oil leaking from hydraulic hose which was detachedat the time when the disassembly operation.
(2)

There was no monitoring person in the middle deck in which fusion cutting spark,etc. fell.
Although the watchdog was appointed, there was nobody on the middle deck whenfire broke out; as a result, it was too late to notice the fire.
(3) The powder in the fire extinguisher did not jet, therefore they failed to extinguishfire at first.
3 pressurizing powder fire extinguishers were arranged in the jumbo drill stand,however, it was reported that all of them did not work well. One reason why they did
not work was that, since the fire extinguisher at that day could stop using halfway,
the pressure was coming out as time past. Secondly, it is possible that the fire
extinguisher might be solidified by the moisture in the tunnel, etc. Therefore fire
extinguisher nowadays will not stop injection even if the lever is released.
(4)

Considerable wind blew inside the tunnel after the penetration.

Due to the penetration of the tunnel whole line, considerable wind blew inside thetunnel. This seemed to promote the fire spread. Even there is some information thatthe speed of wind inside the tunnel was near 5m/second. The cause of the wind was
air pressure difference between pit mouths, and the wind blew from Niigata to Gunmaon that day. Besides, it is recorded that the direction of the wind depends on seasonand weather.
(5) The tunnel extension was very long.
Because of the length of the tunnel (5350m), it was impossible to refuge to the safe
place.
(6)

Emergency report to another workplace was delayed.

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Failure Knowledge Database / 100 Selected Cases

Though the call facility was located in each workplace, there was no record whichshowed the communication by the call facility to another workplace was done. There isinformation that a worker of the demolition of the jumbo drill stand ran to the lining
concrete work place to inform them of the emergency. It is impossible to communicate
by the call facility if there is nobody on the other edge of the line.
(7)

Were there sufficient instruction from the predecessor between the daytime andnighttime worker?
In the daytime work on the fire break-out day, combustibles often burnt by thefusion cutting spark which came from the fusion cutting work of the mounting volt by
the oxyacetylene gas cutter. But it was easy to put out the fire; fire extinguisher was
not necessary, and just hitting by hemp sacks, etc., they can easily put out the fire. It
was uncertain whether such information was succeeded as a precaution or not.
４．Immediate Action
The countermeasure headquarters was established just after the accident occurred,and rescue system was organized by the local fire station and the special rescue crewof the Maeda Corp (it was formed of the people who received rescue training and wore
the oxygen breathing apparatus). However smoke from pit mouth was so intense thatthey must wait in front of the pit mouth. Special rescue crew went into the tunnel
after the smoke went away. Finally all workers were carried out of the tunnel withinfour days, however all were dead.
５．Countermeasure(1)

Combustibles should be removed around the fire. If impossible, they should becovered by the incombustible material.
(2)

The watchdog must be stationed in the fire work.
・Fire can be easily extinguished in most of the case, if it is found when it is small.
・The watchdog must not do the any work except for the monitoring.

(3)

Effective extinguishment facility should be prepared in the fire place.
・Using the hemp cloth to put out the fire is the last means to adopt for fireextinguishing.
・Accumulator fire extinguisher which is strong to the moisture in the tunnel
construction should be arranged.
・The fireplug which utilized water supply pipe should be used at the same timewith fire extinguishers in the tunnel construction.
・Maintenance and inspection of extinguishment facility should be done the5Failure Knowledge Database / 100 Selected Cases

appropriate time.
(4) The tunnel after the penetration must equip with the partition in order to control
wind velocity in the tunnel.
The wind direction and velocity change after the penetration by the difference
between weather conditions of the pit mouths, and the working environment in thetunnel considerably changes. The north wind makes the tunnel cold, dry, and thestrong wind is very dangerous for fire.
・By equipping with the partition, the wind velocity should be controlled.
(5)

The tunnel extension was very long.
・The refuge tool for the individual in the emergency should be arranged at thenumber of the workers.
・The refuge tool for the exchange should be deployed in proportion to the lengthof the tunnel.
・”Kagoi” facility which can stand up the fire should be deployed in the tunnel incase of the worst situation. “Kagoi” facility is the place where workers canescape to in case of the failure of refuge, the air in “Kagoi” facility is sent by airsupply tube and is cool down by a water supply pipe.

(6)

Call facility, alarm facility should be deployed.
・Alarm facility and call facility for simultaneously informing of danger to theworkers of each workplace in the tunnel should be arranged.
・The emergency electric power source should be prepared in order to use callfacility, and alarm facility even in blackout.
・Fireproof electric wire is desirable for the electric wire used for call facility andalarm device.

(7)

The communication between daytime and nighttime should be surely conducted.
In the daytime work on that day, the wood chips in which the oil pressure oilsoaked was ignited many times and put out by hitting by the hemp bag. If suchinformation was informed, the monitoring would be surely carried out in the nightwork, and fire might not be generated.
6． Knowledge
・Combustibles around the fire work should have been removed beforehand. If
impossible, they have to be covered with the noncombustible.
・By stationing the watchdog around fire workplace, the early detection of the fireshould be done.
・The fire extinguisher placed in the tunnel has to be accumulator fire extinguisher

6Failure Knowledge Database / 100 Selected Cases

which is strong to the moisture.
・Other than fire extinguisher, extinguishment facility which utilizes the fireplug
should be used. Besides, the maintenance and inspection should also be executed.
・In penetrated tunnel, t is necessary to control the wind velocity by building apartition in case of the wind velocity is rapid.
・In the construction of the long tunnel, the individual refuge tool (respiratory
protective equipment, anti-smoke glasses, illuminator, etc.) must be deployed
more than the number of the workers.

The refuge tool for exchange on the wayof refuge should also be deployed more than the number of the workers in theappropriate place.
・Call equipment and alarm facility for informing the worker who works in thetunnel in case of emergency have to be deployed.
・Information must be surely transferred between daytime workers and nighttimeworkers.
・To prepare for the emergency, the education and training how to respond theaccidents have to be carried out beforehand.
７．Background
The penetration ceremony of Oshimizu tunnel was held on January 25th, 1979,
about 20 days after that, the full cross section off spread excavation also completed.
Then there was only about 300m-length lining concrete construction left. The tunnel
fire happened when everybody was liable to be careless.
８．Sequel
It was not possible to do the on-the-spot investigation until 3 months after
Oshimizu tunnel fire occurred. This might be evidence that proved how strong thetunnel fire was. And, it was also the fact that legal restrictions for preventing tunnel
fire were lacked in Industrial Safety and Health Law. This tunnel fire encouraged toadd the text about fire and explosion in tunnel construction on Industrial Safety andHealth Law. The facts below seemed to be proven by this tunnel fire.
・ It was thought that that it was natural that the smoke flowed to the workers
who worked in leeward workplace, because they were informed of that there wasa demolition work of the jumbo drill stand on that day. Therefore the workers of
the lee side did not escape, and the work was kept as it had been. This proved
how important the communication system of the emergency was.
・The workers who succeeded in the escape rode on the train. And those who7

Failure Knowledge Database / 100 Selected Cases

missed the train and those whose train derailed failed to escape. Human’s
walking speed is limited, therefore it is necessary to consider the refuge means
such as utilizing trains, etc. in case of the fire in the long tunnel construction.
・The wind inside the tunnel blew strongly, and the testimony that the force of thefire suddenly strengthened was reported. It is necessary to control the force of thewind by equipping partition in penetrated tunnel at the proper place.
・In case of the tunnel fire, the heated air expands and it flows to the closest pit
mouth of lee side, and the fresh air is supplied from the windward. Therefore theflow of the smoke is gradually intensified. This is the chimney effect. It is possible
to observe the similar effect in subway fire in Tegu City, Korea, and the cable car
fire for the mountain climbing in Austria.

It is an iron rule to escape to thewindward in spite of the existence of the escape mask, when the fire breaks out inthe tunnel.
９．On the SideIn May, 1976, the catastrophe which observed 9 persons death by the methane gas
exploding in the agricultural waterway tunnel construction in Yamagata Prefecture.
But, after 2 years, the completely same disaster that observed 9 persons died bymethane gas exploding in the different construction section of the same agricultural
waterway tunnel construction in June, 1978, again. In the Joetsu Shinkansen
construction, the fire that fortunately 20 persons could escape from Nakayama tunnel
broke out in May, 1976. And also there was a fire that 37 persons blocked in Yuzawa
tunnel occurred in July, 1977.

It is safe to say that the human reflection continues

only about 1 year, inferring from that similar disaster occurred in Oshimizu tunnel
construction of the same Joetsu Shinkansen construction. It is necessary to prevent
this kind of accident happen again to freshen up by reexamining the disaster case at
the proper time and to regularize the countermeasure.

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