| Case Name |
The log which had supported the cofferdam panel came off, and the victim was trapped under the panel. |
| Pictograph |
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| Date |
March 23, 1998 |
| Place |
Numata City, Gunma Prefecture |
| Location |
At the new construction site of the public sewerage ( the pipe and drain construction ) |
| Overview |
If we do the backfilling in a state of keeping the trech timbering installed while cutting and covering the groove at a width of about 1.2m and at a depth of about 4.1m depth at the new construction site of the public sewerage ( the pipe and drain construction ), the earth pressure acts the sheeting panel and we cannot pull out the panel.
That is why, first of all, the upper panel was removed, secondly the lower panel was lifted at a height of 1.5m, and the victim centrally inserted one log under the lower panel and he removed the suspension wire.
When the victim threw the woodchip around his feet, he lost his balance and fell down.
Then the log came off, and he was trapped under the panel ( about 710 kg ) that fell. |
| Incident |
Since the victim hit the log which had supported the cofferdam panel, it came off and he was trapped under the panel at the new construction site of the public sewerage at about 1:50 on 3/23 in1998. |
| Sequence |
* In that morning the hume pipe construction and the sandy backfilling were carried out, and from that afternoon the same kind of jobs were going to be carried out at neighboring site.
* First of all the operational procedure of the backfilling usually involved establishing the sheeting panel of the top and bottom two steps in both the right and left sides. However, because the small backhoe couldn't remove the 2 panels simultaneously in the backfilling work, at first it removed and lifted the upper panel.
* It also lifted the lower panel at a height of 1.5m in the same way, and the victim who waited in the groove inserted one log under the panel. And he removed the suspension wire of the panel.
* When the victim threw the woodchip around his feet, he lost his balance and hit the log, and the panel fell on his thorax. |
| Cause |
* Since ,concerning the work plan, only one log's supporting the panel of the lower step was unstable and they had removed the suspension wire of the lower step panel, they carried out the work by the dangerous work method.
* In the backfilling work, the work was continued without letting the victim in the groove take shelter on the ground.
* They had not mastered the construction technology of this method and the safe work method, and they had not carried out the safety education. |
| Countermeasures |
* In the backfilling work, they should adopt the suitable machinery ( crane, backhoe ) designed by the specification and construction process ( the right operational procedure of the simple sheeting method ) .
* They should confirm the work safety and watch the situation of the work when they have workers doing backfilling in the groove for a reason.
* They shoud carry out safety education with workers about the work flow of the method, and precautions and prohibition matters, etc. in the groove work.
* They should teach workers so that the workers may not take the difficult action and posture in the groove work. |
| Knowledge Comment |
* Such a failure would not have arisen, if had they prepared the machinery designed by the specification of the simple sheeting method and had carried out the construction according to the construction process.
* They should observe the fundamental safe construction method and the construction process. |
| Background |
* There were three trunk lines at this construction site and the construction was advanced by the installation of the general trech timbering at the two trunk lines of the other site.However, on the trunk line ( site ) where the disaster happened, theyadopted the simple cofferdam method by considering the landform of the place, depth of cutting, construction period, and so on.
* They didn't prepared the truck crane from the beginning at that time, though this method had been designed that they should usually have prepared the truck crane ( lift load : 4t ). In addition, it was not fundamentally different from the construction process, because they used only one backhoe ( bucket capacity :0.4 cubic meter ) of small capacity.
* At this site, they had succeeded in the way of the square timber only 1 time. That is why, they never had the consciousness to danger. |
| Sequel |
Both the main contractor and the subcontractor lacked the safety knowledge and the experience in order to manage the suitable site execution at the construction site of the sewerage, as they had never excuted the sewerage and the representative of the main contractor had been inexperienced. |
| Incidental Discussion |
Generally the representative of the main contractor had been elected as the trench timbering operation chief, but either the main contractor employee or the subcontractor site manager had led when he had been absent. |
| Account of Concerned Parties |
They had not advised the worker about assembling the trench timbering and securing the safety of in the disassemble work, and they had not given the safety education about the safe work method and procedure. It means that the recognition on the danger in the work was completely lacking. |
| Reason for Adding to DB |
It means that the recognition about the danger in this work was completely lacking. |
| Scenario |
| Primary Scenario
|
Organizational Problems, Poor Staff, Poor Value Perception, Poor Safety Awareness, Regular Operation, Nonobservance of Procedure, Regular Movement, Dangerous Movement, Regular Movement, Careless Movement, Failure, Fracture/Damage, Failure, Large-Scale Damage, Bodily Harm, Death
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| Sources |
http://www.jaish.gr.jp ( Safety and Health Information Center )
|
| Number of Deaths |
1 |
| Number of Injuries |
0 |
| Consequences |
It was natural that the employer of the public sewerage facilities construction lost the confidence, and the employer gave society the distrust for slipshod construction and the fear of the danger. |
| Notes |
In March of 2002 Construction Industry Labor's Accident Prevention Association instituted "the guideline on the cofferdam precedence method" including this method. |
| Field |
Civil Engineering
|
| Author |
KANO, Koji (Japan Construction Safety and Health Association)
KUNISHIMA, Masahiko (The University of Tokyo)
|
