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JICOSH Home > Case Studies > Case No.103
Case No.103

The edge of a trench suddenly collapses during work to inspect an excavated sewage trench
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[Description of the Accident]

This accident took place during work to inspect an excavated trench (1.4 m deep, 24.5 m long and 1.6 m wide) for the construction of a sewer at the construction site of a housing development. When the victim was walking along the edge of the excavated trench, the edge of the trench at his feet collapsed, and he was buried in the trench together with the collapsed earth.

The ground in the area was very soft as the development was being built on the reclaimed land of a former lotus bog that had only recently been filled in. In addition, some 26 mm of rain had fallen just two days before the accident occurred.
[Causes supposed]

1. Walking along the edge of the excavated trench.

2. Installation of soil-retaining sheeting or other measures to moderate the slope, etc., had not been taken.

3. Safeguards such as prohibiting entry into the area, etc., had not been taken in advance.

4. Additional earth was piled up on the edge of the excavated trench.

5. An operations plan for the excavation was not prepared.
[Type of business] Water and sewage construction
[Caused by] Natural ground
[Type of accident] Collapse
[Number of victims] One fatality
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