| Case Name |
Rock collapsed during inspection in the excavation groove. |
| Pictograph |
|
| Date |
1978 |
| Place |
The Nagakute town in Aichi Prefecture. |
| Location |
Residential land development construction field. |
| Overview |
Suddenly the graverock collapsed when a worker entered into the groove to see the roughness of excavated slope while they were drilling the base of retaining wall with 5% gradient. |
| Incident |
Suddenly the graverock collapsed when a worker entered into the groove to see the roughness of excavated slope while they were drilling the base of retaining wall with 5% gradient l. |
| Sequence |
The site had been drilled 3 months before, and work restarted on the backing excavation of the block pattern of the 5 minute gradient and 4.5m height folowing the accident occurrence the previous day. The victim directed the work, and worked with the operator of the backhoe ( 0.7 cubic meter ). On the previous day, the victim had instructed the operator to drill the rock roughly about 1.5m in depth , the accident day , and they did same work in the lower part. Simultaneously, basic excavation ( 1.5m depth and 2m width ) of block pattern had also been done the accident day. The victim was to observe the condition of the ruggedness of the excavated slope from under the slope, stopping the backhoe ,when suddenly the rock collapsed from the upper part, and he died under the gravel. |
| Cause |
The preliminary survey and reinvestigation before the commencement were insufficient. The inspection of the rock under construction was insufficient. The risk awareness was insufficient. The country rock suddenly collapsed. They checked the slope from the groove. |
| Countermeasures |
Check of in-situ rock must be done under the construciton and during the construction.
Work must be done with positioning the excavation chief of in-situ rock .
Re-check of TIYAMA left for 3 months must be done as the first time of drilling.
Education and training of the safety and sanitary must be done. |
| Knowledge Comment |
Drilled country rock may suddenly collapse. In a dug hole, the danger of decay is hidden. In the case of the work needing a qualified person, the qualified person must be present. |
| Background |
The condition was thought to be safe for 3 months and the previous day too.
The survey result that it was the very hard rock was shown. |
| Scenario |
| Primary Scenario
|
Insufficient Analysis or Research, Insufficient Prior Research, Ignorance of Procedure, Disregard of Procedure, Poor Response to Change in Environment, Change in Environment, Carelessness, Insufficient Understanding, Malicious Act, Rule Violation, Regular Movement, Dangerous Movement, Failure, Large-Scale Damage, Bodily Harm, Death
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| Sources |
Disaster case, KENBOUSAI Aichi. VOL.S54.1.1
|
| Field |
Civil Engineering
|
| Author |
IKAI, Seiji (ICHITEC CORPORATION)
BABA, Kanji (ICHITEC CORPORATION)
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