Wednesday, April 29, 2015

Unshored Trench Stability

The picture has been cut from global news without permission.

The man was playing unshored trench roulette. He lost. Note that the banks are still calving on the left. There is a block on the dropped in shoring at the tip of the hoe boom.

Note that much, if not all of the shoring carries the fire department yellow.

He or his bosses gambled on a win of time against death. No job is worth taking a risk like this for; especially for wages. He may be in a "do it or we will find someone who will" situation. Until Alberta puts a whistle blower protection in place, or "no fire" over refusal to do unsafe work policy, with investigation, and teeth, the problem will continue. Firing someone or even asking anyone to do unsafe work should carry a major fine, and be religiously prosecuted on the governments dime, to have any effect with shoe string contracting companies. 

OH&S regulations state no entry into a straight cut trench deeper than 1.5 meters, or 45 degree back slope with 1.5 meter bottom straight cut in undisturbed native clays.

The spill pile is too close, 1.2 meters required, by OH&S.

It is fill, not clay. We can see the garbage and bricks in the spill in the new report video. OH&S therefore does not apply. The strength of fill is unreliable, therefore expect failures.  

This is not quite straight cut, but it is steeper that a ladder likes, about 70 degrees so I will estimate 80 degrees. It does not matter, it grossly exceeds OH&S.

It is my opinion that OH&S rules are not rigid enough as it stands. But if they were followed, we would have far fewer injuries and deaths. In all my years in geotechnical, I have only seen a few cases where failures occurred within OH&S rules, and these were blocky and/or slickensided soils, large or deep excavations, or long term conditions.

It is my opinion that everyone involved should be charged with manslaughter, general contractor, trench contractor, and hoe operator. There should be a mandatory course required for anyone entering a trench, or pushing a trench job. Major fine for doing the work without the card.

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