Let's say I have a mountain range similar to the Andes but with no easy passes, hence forcing everyone to circle around it (for hundreds or even thousands of miles) in order to get to the other side.
I want to cut through it where it's easier: high enough that the area to cut through is no longer than about 40 miles / ~64km (taking Moria as an example) but not high enough that even getting to the entrance becomes difficult. It will be comparable to the upcoming Turin-Lyon high-speed railway.
At first, it needn't be anything more than a wide tunnel that allows four carriages to pass through (let's say 12 meters wide and 4-5 meters tall) but we will want to expand it so that workers' housing can be built in the underground passage itself (and, over decades or even centuries, become a city somewhat comparable to Moria). The tunnel can be wider if need be, e.g. for transporting excavated rock outside.
Also, it might have a slight ascending slope, so that bringing rock outside gets easier (we could have full carts go downhill, and empty cars be pushed uphill)
Of course, the most livable areas will be those close to the two entrances, but I suppose people will be able to inhabit the middle section of the tunnel too as long as getting food and supplies there isn't a problem.
A few notes:
- technology is comparable to that of 14th century Europe
- the nation/kingdom/faction doing the excavation doesn't control the territory on the other side of the mountains, so it can only dig from one side (and not from both simultaneously). Assume that attacks from the other side are not a problem, though.
- the nation/kingdom/faction doing the excavation knows (and uses) various kinds of food that can be grown underground. So assume that growing food is not a problem.
- assume that safety from attacks (wild beasts or other factions) is guaranteed
- they need some way to improve air flow
- workers are dwarves who can see even in total darkness up to 60 feet away (in black and white), so lighting is not a problem
If availability of manpower is not a problem (let's say we can field as much as 100,000 dwarf workers, but it can be much fewer if that high a number creates more problems than it solves),
- how long would it take them to dig through 60km of rock and dirt?
- what would be the greatest difficulties in doing so?
This question is very interesting, but is more about "how could dwarves survive in such a city" while I am interested in the making of.