Eli5 Big piles of rocks and dirt at construction sites?


How do they make the gigantic piles of rocks you see at construction sites? There’s some construction taking place near me and the pile of small rocks and dirt has to be a good 50+ feet tall to the very top, and its like mountain shaped. How does that happen? Does the bulldozer just keep pushing it all together and it keeps getting taller? Doesn’t it become a safety hazard for it to all collapse and bury the bulldozer? Im very confused about it, the pile in question seemed to have appeared overnight.

In: Other

They are probably using mechanized/hydraulic shovels, that can get quite high depending their size. And you normally pour the soil with care, to avoid too much pebbles and cobbles rolling down the pile.

Pyramid/cone shapes tend to be pretty stable without using any reinforcement technique: that’s why early civilizations liked them so much.

Guy who works on a construction crew here. Dirt can actually be really dense. On a recent job we were putting in a wooden fence and we had to dig the post holes with a post hole digger and it’s a real pain in the a**. You only go down like 2 feet but it can make a very large pile. Reason being is when it’s in the ground, the dirt is constantly being compressed and stepped on making it very dense. But when you take it out of the ground it often crumbles and that makes it much less dense. So that’s why there’s so much dirt. How it gets there, there’s a couple things that could happen. In my situation when I was digging the holes on such a small scale you just use tools to get the dirt out of the grounds, but for the larger scale ones then you would use a large bull dozer, probably some trucks, or maybe even a crane. It all depends tho. The reason it looks mountain shaped is because you just dump it out in the middle and over time as you do that some pieces trickle down to the sides bc of gravity and that’s that. Lmk if something doesn’t make sense! Hope this helped!

We have [piles of rocks](https://upload.wikimedia.org/wikipedia/commons/a/af/All_Gizah_Pyramids.jpg) that have been stable for a lot longer than most construction projects the shape is naturally the most stable. It’s probably not a smart idea to go climbing a randomized pile of rocks until its had a while to really settle into the shape but the [shape a pile makes](https://images.unsplash.com/photo-1518281361980-b26bfd556770?ixid=MnwxMjA3fDB8MHxzZWFyY2h8Mnx8aG91cmdsYXNzfGVufDB8fDB8fA%3D%3D&ixlib=rb-1.2.1&w=1000&q=80) as particles are dumped on it is pretty uniform. Just a question of how well the bits stick together or flow around each other to decide how steep the side is. (I think others have covered what machine may have created the pile exactly.)

The other thing is if something was previously at the site (houses/buildings), they often demolish and on-site grind concrete/brick with a portable version of the same equipment quarries use to create quarried stone. It comes with ramps that can pile the demolished brick/concrete into very high mounds.

Then when they’re ready, they can reuse it on-site as surface grading material instead of having to truck it off-site for disposal.