Remember burying a friend (or being buried) in sand while playing at the beach? Maybe that image is one reason why it’s easy to underestimate the danger of being caught in a trench collapse at work.
Sure, the soil might cave in, but so what? Unless it’s a huge cave-in, you’d just dig yourself out, right? The reality is far different. In fact, it’s sobering. When it comes to trench collapses, earth is definitely not friendly.
You don’t have to be in an especially deep trench to be seriously injured or killed in a cave-in. In fact, you can be seriously injured or even killed if buried in soil only to your waist. That’s because of the way cave-ins occur, and simply because soil is heavy.
Powerful momentum
Picture a cubic foot of soil. How much would you think it weighs? Typically, it weighs about 100 pounds, and it can weigh even more depending on its composition and how much moisture it contains.
Now imagine a cubic yard of soil. It contains 27 cubic feet, which means it weighs 2,700 pounds – as much as a mid-sized car. It’s not at all unusual for a cave-in to involve a cubic yard of soil, or much more.
An excellent safety tutorial on an Auburn University College of Continuing Education Web site, www.trenchsafety.org, describes the hazards of cave-ins. “Once precipitated, a cave-in is lightning fast,” says one lesson on the Web site.
“Unstable soil flows quickly like a fluid into the trench opening, exerting extremely high pressures on anything in its path. This creates a serious life-threatening hazard for workers in the trench.”
The momentum of collapsing soil could knock you over, or even break bones. Once you’re covered, pressure from the soil can hinder blood circulation to your arms and legs. Even if buried only to your knees, you would have difficulty digging yourself out, and in the meantime circulation could be cut off.
“A person submerged under only a couple of feet of soil would experience enough pressure on the chest area to prevent their lungs from expanding,” the Web site says. “Suffocation would take place within about three minutes. Even if the person is rescued in time, the heavy soil loads are likely to inflict serious internal injuries.
“A person buried in earth as high as his diaphragm, would not be able to dig himself out, and his chances of survival would be low. If the face is even partially covered, death is almost certain.”
Hazards of rescue
What’s more, once you’ve been caught in a cave-in, getting you out is a delicate operation that requires training and skill. Many victims of trench collapses are further injured or even killed by panicky co-workers trying to dig them out with shovels, or even heavy machinery.
To make matters even worse, rescue workers entering an unshored trench face the danger of further soil collapses. That’s why, if the victim of a collapse is trapped but breathing and stable, the response team will shore the trench before finishing the rescue.
Excavation cave-ins are a serious problem. The Trench Safety Web site says that from 1990-2000, 771 workers died in accidents involving excavations in the United States. “Moreover, for each excavation fatality, perhaps 10 times as many workers are injured, some of them with serious long-term disabilities. The real tragedy is that most if not all excavation accidents are avoidable.”
The Auburn Web site provides an 11-lesson tutorial on all aspects of trench safety. If your employees’ work involves trenching, this Web site is an excellent resource for teaching about the hazards and how to avoid them.
