Cave-ins during an excavation is the greatest risk that could happen and is actually more likely to occur than any other common excavation site dangers and hazards. Because cave-ins are often fatal incidents, regulations and industry best practices were specifically created to prevent them and protect workers on the job.

Think of it as similar to a large-scale shaky sandcastle with its walls crashing in on itself, where one cubic yard of soil almost weighs as much as a car – heavy, right? It happens really quickly too and whoever is within those walls will definitely either get buried or trapped, given that there are no safety measures to prevent cave-ins. With all that heavy weight on top of the trapped workers, it gets even harder to escape and get air for breathing.

There are key protective systems that workers and on-site personnel must do to prevent cave-ins during an excavation:

Don’t place heavy equipment and vehicles near the edge: It’s common sense, but sometimes people on site tend to forget that because it’s easier to have everything accessible and visible from within the vicinity. However, the more weight you put on the edges of a trench, all the more that very weight pushes down on the soil. And that’s worse when the soil is already fragile to begin with because of the excavation depth and other factors. When those edges collapse, it’s not just the very equipment and vehicles that fall over, it also includes the surrounding areas – it’s a dangerous domino effect.

Set back safe zones: In addition to avoiding putting weight on edges, this prevention method ensures that personnel and other equipment are placed at a certain distance away from the edge to make sure nothing and no one gets dragged along when the edges and the surroundings collapse. The solid rule of thumb is: if the trench is 5 meters deep, then set the safe zone at least 5 meters away from the edge. Don’t just set it via word of mouth, mark the safe zone/distance with barriers and warning lines, so no one drives or parks near the excavation site.

Cut the trench walls at an angle (slope) or with steps (benching): Instead of a cliff type of digging, cut at an angle or with steps to make the edges more stable and less likely to collapse. The goal is to avoid putting so much pressure on the walls that they collapse. Sloping is ideal for when there is a large space to slope the digs, but if there is not enough space, then benching is the second-best option you could go for.

Add supports along with sloping/benching: This is probably the safest and most practical option – to combine shoring (adding supports) along with sloping/benching. Shoring is installing supports like metal and timber right along the trench walls. It aids as additional support to keep the soil in place, like on one side you could be sloping and on the other side you’re shoring. A good combination would be that if the upper layers of the soil are firm enough, but the lower layers are loose, it’s best to slope the top and then shore the bottom. Two key things to remember is to (1) check in with the local safety standards that you follow to see whether mixing methods are allowable, and (2) have a professional conduct a site-specific soil analysis to determine the conditions of the soil, and then identify the mixed methods for support.

Conduct regular inspections when conditions change: It’s always a given to inspect the soil conditions after anything that affects it, like rain, heavy winds, soil movement, etc., including the walls, and all of the supports. If the weather and seasons change in the duration of the excavation job or changes are normal in the site location, it’s just better to be safe to inspect before workers go on about their days than to be sorry accidents occurred.

More dangers to be wary about are laid out in this article Excavation Hazards and Control Measures, including the appropriate control measures to lighten the risks.

Having this highly dangerous consequence of not following the standards, regulations, and guidelines, it should be more than enough to convince practicing excavation safety.