Reinforcing an Underground City

[Surzt and Gurzt]

How would an underground city like the Drow's fortify itself against earthquakes, stone-shaping druids and other dangers of underground life?

I recently introduced my PCs to a city built into massive stalactites/stalagmites , and I would like to make it seem that the city planners had, well, planned for this thing. Bonus points if your solution is as low-magic as possiable.

[Otomodachi]

http://en.wikipedia.org/wiki/Earthquake_engineering

Teach a person to fish...? :P

I kid, I'm reading through this while I work, I'll add an edit with an attempt at a useful distillation soon as I have one, but I figured you might want to check it out as well. :)


Edit-
http://en.wikipedia.org/wiki/Earthquake_engineering#Dry-stone_walls_control

I think this is what you want. Imagine over the course of a few years, support columns were cut down and replaced with slotted-but-not-mortared stacks of blocks, one at a time. It's low-tech, it uses available resources.

Also, apparently tall structures that are vaguely pyramid-shaped are more resistant to toppling, so make sure all your look kinda like this guy http://upload.wikimedia.org/wikipedia/commons/thumb/5/5f/TransamericaPyramidFromTI.jpg/246px-TransamericaPyramidFromTI.jpg

Bonus points for that one in that you can say that the pyramid shape helps guide ley lines, or something suitably mago-babbly. ;)

[Clawhound]

Adamantine-laced rock.

You could also have spider-silk webs crisscrossing the main city so that anything falling hits the incredibly strong spider silk.

Perhaps the city could have a specialized spell that deflects falling debris. Forcefields would make sense.

A partial dome/cone could also work.

Maybe a spell which telekinetically moves slaves in front of any falling debris, thereby saving drow homes from harm.

[Demonic_Spoon]

A few 24/7 lyre's of building? otherwise walls of iron everywhere along with some reinforcing from the humble but ever useful wall of stone.

[Otomodachi]

Adamantine-laced rock.

You could also have spider-silk webs crisscrossing the main city so that anything falling hits the incredibly strong spider silk.


I thought about adamantine, but I know just enough about engineering to know I don't know enough about engineering. I decided maybe a metal that is very strong in one sense would not necessarily be superior when it comes to not shattering due to vibration. :/

The spider web idea, however, is awesome- enough webs between support columns, and structures, and you'd be spreading out the kinetic energy from the vibrations, right? And it's wicked thematic for the underdark.

I also considered pools of mercury surrounding the base of each support structure, but that stuff is pretty toxic.

Edit: Guys, if there's one thing I've picked up from my research, it's that the structures HAVE to wiggle. Trying to strengthen them not to wiggle will cause them to sunder. I don't think sturdier walls are the answer. There's no level of sturdiness that can't be broken apart by vibration, apparently. :/

[paddyfool]

I like the idea of the spidersilk supports... particularly if they doubled as walkways. On which the vibration of non-Drow-like steps would alert spiders trained to accost interlopers and/or escaping slaves.

[Aeryr]

Edit: Guys, if there's one thing I've picked up from my research, it's that the structures HAVE to wiggle. Trying to strengthen them not to wiggle will cause them to sunder. I don't think sturdier walls are the answer. There's no level of sturdiness that can't be broken apart by vibration, apparently. :/

Yep it's been stated and studied... here, take a look http://www.youtube.com/watch?v=j-zczJXSxnw (it's a classic example)

Personally expanding on the spider silk idea you can get a "fallen" city on a humongous web over a lake. The city originally was on stalagmites over the lake, due to the drow throwing their stuff to the lake several spiders started to spin webs under the city, trying to get the juicy bodies. The city and the spiders started a symbiotic relationship, the drows dumped enough food for the spiders to live comfortable and the spiders provided mounts/guards/pets/silk to the city. After long years there was an earthquake and some of the buildings carved on the stalagmites fell on the web. The holding of the houses is reinforced with adamantine chains nailed to the walls and some of the more adventurous drow or some pressed outcast moved to the rest of the original city, taking spiders with them, so there is spider web at the top too.