| Case Name |
The concrete block fence collapsed during the groove excavation work. |
| Pictograph |
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| Date |
January 26, 1999 |
| Place |
Miyazaki City, Miyazaki Prefecture. |
| Location |
The construction site to build a new one-story house on a steel framework. |
| Overview |
Two concrete block fences (height: 2.2m) in east-side and north-side collapsed suddenly, and four workers were crushed under them when workers excavated a groove (width; about 2.0m, depth; 1.1-1.4m) by using a drag shovel (weight; 4.05t) to excavate a groove for the base of a one-story house on a steel framework. |
| Incident |
On January 26th, 1999, at about 16:40, in the construction site to build a new one-story house on a steel framework, two concrete block fences (height; 2.2m) collapsed suddenly (east-side fence collapsed over 17..m, north-side fence collapsed over 11.0m). So, 4 workers, who were leveling the ground, were crushed under them. Two people died and the other two people received serious or slight injuries. |
| Sequence |
* On the morning of that day, they had excavated a groove for the base (width; 2.0m, depth; 1.1-1.4m) using the drag shovel, toward north-east side from north-west side, inside the boundary line on the site.
* In the afternoon, after the work at the east side, they had excavated the groove about 17.0m, from the edge of the north-east side toward the south side, along the concrete block fence. They forwarded the excavation to the point near the termination.
* At that time, concrete block fences (height; 2.2m) collapsed suddenly, over 2 sides of the fence, one was from the edge of south-east side to north-east side, another was to north-west side (east side; about 17.0m, north side; about 11.0m).
* Four workers who were at the north side were crushed under them. |
| Cause |
* The earth-retaining wall had not been established in the ground of the concrete block fence base at the edge of the south-east side. So, this part collapsed first, and other fences collapsed one after another because of the linkage of the weight.
* At the place which was close to a work object like a concrete block fence, they carried out the excavation for the base. But, they didn't take any countermeasure to reinforce it.
* They didn't survey excavation places in advance. They didn't make the work planning mannual, for example, operational procedures, the way to work, and so on. They depended on the foreman's intuitions. |
| Countermeasures |
* They have to confirm the situation of the construction site by the survey in advance or the preliminary excavation. For example, the years of masterpieces such as a fence, the structure of a fence etc, existence of bar arrangement, situations of the setting of the base, the working diagrams of excavation depth.
* They have to examine collapse prevention measures, such as reinforcement methods for concrete block fences (installation of sheeting walls and duplicates, etc.) or removals of a part of the fence. And they must adopt the safest construction method.
* They have to determine the excavation work planning, set operational procedures according to it and the zone to prohibit entry, and take other countermeasures to prevent danger.
* To have related workers know the work plan, and to work safely under the integration management of the contractor. |
| Knowledge Comment |
* Don't forget to take reinforcement measures for work objects such as a concrete block fence!
* Be true to safety work! Don't depend on the foreman's intuition etc.! Make a careful work plan! |
| Background |
* This method relied on the autonomy of a concrete block fence, and they didn't take reinforcement methods. There were basic problems that caused the collapse accident.
* The problem is that the groove excavation by the drag shovel operator and the leveling work by the foreman and workers were carried out at the same time, so, every worker didn't notice the signs that the concrete block fence was going to fall. The background is that there had not been any knowledge education about such problems.
* There wasn't the person of the contractor who had responsibility for the construction site and the person of the subcontractor who had responsibility for the construction site. Both of them are to blame. |
| Sequel |
* The executive punishment was executed by the chief of Labor Standards Inspection Office. It brought first subcontractor and second subcontractor to account for their management responsibility. |
| Account of Concerned Parties |
* They thought it was dangerous to excavate the groove which depth was 1.4m near the fence because the height of the concrete block fence was 2.2m. Then they constructed the earth-retaining wall (the thing which combined with the steel pipe pile) from north-east side to 11.0 point. But it was insufficient as a reinforcement measure. |
| Reason for Adding to DB |
* This paper was written to take prevention countermeasures for the same kind or similar disasters! |
| Scenario |
| Primary Scenario
|
Misjudgment, Misjudgment of Situation, Organizational Problems, Poor Management, Poor Value Perception, Poor Safety Awareness, Insufficient Analysis or Research, Insufficient Prior Research, Malicious Act, Rule Violation, Regular Movement, Dangerous Movement, Failure, Large-Scale Damage, Bodily Harm, Death, Bodily Harm, Injury
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| Sources |
* Safety and Health Information Center (The labor accident case).
|
| Number of Deaths |
2 |
| Number of Injuries |
2 |
| Physical Damage |
A collapse of the concrete block fence |
| Financial Cost |
unknown |
| Economic Loss |
unknown |
| Consequences |
This labor accident clearly shows the absence of management responsibility of the contractor and the subcontractor, and the slipshod situation of the safety management in a construction site. And, they are connected to trouble with the client and the loss of social confidence of the enterprise. They also bring bad images of the construction industry. |
| Field |
Civil Engineering
|
| Author |
KANO, Koji (Japan Construction Safety and Health Association)
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