| Case Name |
The earth-retaining wall equipped the slope collapses. |
| Pictograph |
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| Date |
June 9, 1997 |
| Place |
Akita Prefecture. |
| Location |
Leg foundation work field of steel tower in new transmission line . |
| Overview |
This disaster occurred in the steel tower leg foundation workfield of new transmission line. There were two earth-retaining wall(upper and lower). In order to change the arrangement of the walls, they were working to remove the lower one. Then, 5 square meter of mud supported by the upper wall collapsed and 3 of 4 workmen who worked below were involved in the gravel. |
| Incident |
The ridge in the mountain was installed so that the leg may stride on the steel tower ( about 60m heights ). In this steel tower leg foundation work, the earth-retaining wall was founded for the security of embankment place and road for the heavy machine running in the slope under the leg. Two earth-retaining wall was installed under removal work and the upper stage side collapsed ( gravel about 5 square meters ( 1.5m height, width about 8m ) ), and 3 of 4 earth worker who were engaged in the removal work in lower step under the slope were involved in the gravel, and suffered then forced to rest. |
| Sequence |
Workability was bad ,so the review was made on the arrangement of the road for the heavy machine selfpropellent, since morning. They decided that "First earth-retaining wall" would be removed, and they set about this work, but the responsible person reached the field afterwards, then directed the change of the arrangement again, then "Second earth-retaining wall" was being removed next time. Then , "First earth-retaining wall" collapsed, and embankments about 5 square meters supported by the upper wall collapsed, and 3 of 4 earth worker who were engaged in the removal work were involved in the gravel. |
| Cause |
The strength of the earth-retaining wall was installed without sufficient strength calculation at founding phase. The position of the earth-retaining wall was changed again and again , hoop and safety were not sufficiently examined, and was constructed , while there was no assembly diagram either. Since earth pressures, etc. exceed proof stress of earth retaining wall, as the result, it came to the decay. |
| Response |
The new earth-retaining wall was founded after the restoration. |
| Countermeasures |
In the design of the earth retaining wall, Do check the sufficient strength for earth pressures, etc.. In addition, they must make "assembly diagram" that has arrangements, dimensions and materials, order of the mounting of the member, etc. And it must be carried out correctly. |
| Knowledge Comment |
In comparison with the main body structure, the temporary structure is apt to be slighted. Based on the preliminary survey, earth-retaining wall of the sufficient strength have to be designed, with safe and efficient work planning, and it is constructed under the appropriate assembly diagram. The construction must be undertaken, after safety, etc. is confirmed, when the plans of temporary earth retaining wall's position, etc. are changed. |
| Background |
There were no examination or calculation of the strength of pressure from muds on earth retaining wall and the tension on wire, etc. Their decision was made on the easy intuition. The imperfection of work planning. The imperfection of the safety management system. |
| Reason for Adding to DB |
The frequent occurrence of gravel decay disaster under the construction developing. |
| Scenario |
| Primary Scenario
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Insufficient Analysis or Research, Insufficient Prior Research, Poor Response to Change in Environment, Change in Environment, Organizational Problems, Poor Management, Poor Value Perception, Poor Safety Awareness, Ignorance, Insufficient Knowledge, Planning and Design, Poor Planning, Production, Hardware Production, Non-Regular Action, Change, Failure, Large-Scale Damage, Bodily Harm, Injury, Loss to Organization, Economic Loss, Loss to Organization, Social Loss
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| Sources |
http:/www.jaish.gr.jp/
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| Number of Deaths |
0 |
| Number of Injuries |
3 |
| Physical Damage |
The decay of the earth-retaining wall. |
| Field |
Civil Engineering
|
| Author |
TOYOSAWA, Yasuo (National Institute of Industrial Safety)
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