How do REALLY old underground structures like Roman’s acqueducts dont collapse?

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Hello, I’ve always been curious about how ancient underground tunnels and structures, such as the Roman aqueducts and Ancient Egyptian tombs, managed to avoid collapse or dangerous cave-ins. I’ve searched online but found limited information.

I’m particularly interested in understanding what materials and techniques were used to reinforce these structures and how it was done. For instance, did they build brick walls or simply cover everything in concrete? Any insights would be greatly appreciated. Thank you!

In: Engineering

4 Answers

Anonymous 0 Comments

A common adage in engineering is “anyone can build a bridge that stands up, but only an engineer can build a bridge that barely stands up.” The idea is that with a lot of modern construction the goal is to build a thing that’s safe and does its job, but minimizes unnecessary costs.

For a lot of Roman and other ancient construction, they simply didn’t do that. They didn’t have the materials knowledge that we have today, so everything they built wound up being built way, way, way stronger than it needed to be. They didn’t use any particular special techniques, but rather because they didn’t have the techniques we do today they used brute force to have confidence in the stability of what they built that we can get much easier today.

That said, their structures didn’t all last the test of time. We just typically pay the most attention to the ones that did.

Anonymous 0 Comments

Underground structures displace the load to the sides so there is very little pressure on them to collapse and a simple stone structure can take the load.

Anonymous 0 Comments

A common factor for all those ancient structures you mention is survivorship bias. The ones you see now have survived and you don’t see the many that have failed.

Anonymous 0 Comments

Masonry – bricks and stone – are incredibly strong under compression. Mountains can reach over 8000 metres high. Masonry is however weak under tension – twisting forces, which is a problem for building a roof. Arches are a way of converting tension forces to compression forces and thus are very sturdy. If you *want* to break an arch, perhaps blowing up a bridge while retreating from a military, you need to break it in three parts.

Unfortunately putting windows into walls introduces tension forces around the window. Also, if you want to bridge a sizeable river with a masonary arch, you either need to build a massively high arch, which requires long earthworks on both approaches to make it possible to haul a cart over it, or you have to build multiple arches into the river, which is expensive and interferes with river traffic.

Thus olden-day builders often use wood, which is good at taking tension but does deteriorate over time. In modern times, builders use steel but that’s after a number of technical breakthroughs in the 18th and 19th centuries meaning steel could be produced cheaply en masse. The Ancient Romans didn’t have those.