My question is as the title put it. I would like to know how large and thick of a wall we could currently construct. Given we have no limitations in money or materials. Bonus if it's actually sturdy though I don't have much hope of that in this regard. Rooms and hallways are allowed as long as they do not compromise stability and functionality of the wall. Keeping things out is its functional reason for being of course.

I searched for other questions akin for this. Didn't find anything exactly to my needs. As such I'm asking.

  • $\begingroup$ Solid wall, or is it allowed to have spaces/rooms/hallways/etc inside? $\endgroup$ – Andon Apr 22 '17 at 12:54
  • $\begingroup$ Also which is better, something that is thicker while not being as tall, or something that is taller while not being as thick? $\endgroup$ – DonyorM Apr 22 '17 at 12:56
  • $\begingroup$ Clarified. I think that should help. Though any answer is a good answer. $\endgroup$ – Warm Shadow Apr 22 '17 at 13:17
  • $\begingroup$ I don't think thickness would have a limit beyond availability of materials, just height $\endgroup$ – Kilisi Apr 22 '17 at 13:28
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    $\begingroup$ What is the purpose of the wall? Who or what are you trying to keep out? $\endgroup$ – apaul Apr 22 '17 at 13:57

Defensive walls are built on solid foundations. There is no engineering constraints on thickness beyond the availability of materials and the foundation to support the weight.

Height is the real limiter, but if you look at the large pyramids in Eqypt, you can basically have as high as you want as well so long as it slopes from the base rather then being vertical. I would think a wall 3/4's as high as the big Pyramid would be more than sufficient and would have a large flat top that could be further crenelated etc,.

51 degree slope is what the big pyramid used and considering it originally has casing stones it would be very difficult to assault. You could use a much steeper slope, it would all come down to how much weight the materials at the bottom and the foundation could support. The less steep the slope, the more the weight is spread.

If you want to be a bit more modern and use reinforced concrete bricks and a vertical wall then it depends on how you do it. With no bracing high end is 36 times as high as your base is thick or if you use working stress or ultimate strength design there is no height limit, but a lot of other factors need to be taken into account for that. With bracing the sky is the limit.

Solid concrete can be as thick and as high as you want, e.g., the Hoover dam, but even though built on solid rock the dam deformed the crust of the earth and caused several earthquakes due to its weight.

  • $\begingroup$ Can you link to a citation of Hoover Dam causing earthquakes? And how do you know it’s not the weight of the lake it created, which is much larger? $\endgroup$ – JDługosz Apr 22 '17 at 19:44
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    $\begingroup$ @JDługosz Once structures get to the size of mountains, however, isostasy comes into play. $\endgroup$ – Spencer Apr 22 '17 at 20:28
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    $\begingroup$ A hard physics limit on the height is the pressure at which building materials will lose mechanical properties. This is what limits the height of mountains on Earth to something on the order of 10 km. $\endgroup$ – Maxim Umansky Apr 23 '17 at 0:22
  • $\begingroup$ @MaximUmansky nice point, it would also have serious affects on the weather system at anywhere near that height. $\endgroup$ – Kilisi Apr 23 '17 at 0:25
  • $\begingroup$ @MaximUmansky While there is a ~10km height limit due to mechanical properties, there is likely a lower limit based on erosion from glacial formation (follow links from this discussion). Either way, I'm not sure even modern humanity could stack rocks that high. $\endgroup$ – kingledion Apr 24 '17 at 19:33

Diomond base should be able to hold at least 10 times what stone can, so take mount eiger (a mountain with a very steep face) and multiply it's hight by 2.15443469003. That would get you a minimum wall hight of 8,500 meters.

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    $\begingroup$ It's not clear why you multiply by this specific number. $\endgroup$ – frodoskywalker Apr 23 '17 at 11:59

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