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Case No.27


Worker killed when muck car broke free from battery-powered locomotive and ran out of control at the tunnel construction site.
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[Circumstances of the Incident]

This accident occurred during tunnel excavation work that was being carried out by a shield-tunneling machine.

The mud-shield method being used at the tunnel construction site involved excavations at the cutting face by a shield-tunneling machine, segment erection work, muck transportation by a battery locomotive and muck cars, and mucking work from the entrance shaft.

On the day of the accident, workers started operations at 20:00 and  took a rest break at 20 minutes after midnight. The locomotive operator came to the resting room after changing the make-up of the train into the locomotive and a muck car.

At around 1:00, two segment workers, a surveyor and the shield machine operator entered the tunnel to restart their work at the cutting face.

The locomotive operator got into the train at the shaft entrance and backed the muck car towards the cutting face. When the train came to the pithead, the muck car suddenly broke free from the locomotive and started running down the 4-percent grade towards  the cutting face.

The car brushed against a segment worker some 59 meters from the pithead, ran over a surveyor and crashed into the shield machine operator at a point close to the cutting face, finally derailing and coming to a stop around 109 meters from the pithead.
[Causes]
The following can be considered as the causes of this accident.

1 The locomotive operator failed to insert a connecting pin into the coupling after changing the make up of his train into the locomotive and the muck car. This was the reason the car broke free of the locomotive coupling at a point where the 4-percent grade started and ran out of control .

2. As a rule, cars are prohibited from running in the tunnel when workers are working in the tunnell, and workers are prohibited from entering the tunnel when cars are running.  However, the locomotive operator moved his train into the tunnel despite the fact that he knew that workers were passing through the tunnel. Moreover, the shield machine operator and the locomotive operator failed to observe the rule that they must communicate with each other by interphone before entering the tunnel or when they can enter the tunnel.
[Type of business] Tunnel construction
[Type of accident] Crush
[Number of victims] One fatality and one injury requiring an absence from work
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