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I keep seeing these large rectangular structures on job sites they put in the ground.

image

I'm guessing something for strengthening the surface structures?

Wasabi
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v15
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    I believe this is a trench shield or steel trench box, which protects workers from cave ins while working on utilites –  Mar 05 '20 at 17:37
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    Ahh!!! That's it! Thanks! If you put it as an answer, i'll mark it as such. –  Mar 05 '20 at 17:40
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    Yep. And despite them being required by OSHA (I think), you'll still come across an operation where they are not being used. Usually shows up on the evening news when a worker is buried due to a wall collapsing. –  Mar 05 '20 at 17:41
  • I'm voting to close this question as off-topic because this isn't about home improvement. – Daniel Griscom Mar 06 '20 at 02:24
  • Is there another meta site you can move this too? Looking at the views and up votes it appears to be useful information –  Mar 06 '20 at 02:28
  • Note that some people might call it a caisson, though that term more properly refers to a water-tight box. – Hot Licks Mar 06 '20 at 02:44

2 Answers2

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It is a trench shield. It gets placed in a trench after the trench is dug to prevent workers from being hurt or killed in the event of a trench collapse.

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This picture from GMC trench shield shows a partially collapsed trench with a shield installed that would protect the workers installing the blue brute pipe.

JACK
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  • I remember 2 instances where a person lost his life due to that person going into or working in a trench where one of those supports was on the job but not used. One such accident happened at a job near Philadelphia, Pa. and one happened at a job site north of Pittsburgh, Pa. –  Mar 06 '20 at 14:48
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It is shoring for trenching work.

If a trench collapses on a worker the weight and force of the material will lead to crush injuries. Even if you are able to dig someone out from a collapse, crush injuries can lead to crush syndrome ending with kidney failure and death.

Fresh Codemonger
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