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Three questions: 1. Is the Paris Metro so shallow because of the quarries? 2. Do mushrooms still grow in the quarries? Has anyone checked recently? 3. When i

Three questions: 1. Is the Paris Metro so shallow because of the quarries? 2. Do mushrooms still grow in the quarries? Has anyone checked recently? 3. When is a Tim Traveller's video on the subject coming out?

kergonath 2y ago
> Is Paris Metro so shallow because of the quarries? The Paris metro is a mixture of deep, subsurface, and surface tracks. There are a lot of shallow tunnels mostly because cut-and-cover was easier and cheaper than digging deep underground. Paris is very complicated underground. Besides the quarries there are the sewers, catacombs, some underground lakes, reservoirs, etc. It is definitely a complicating factor when planning new metro tunnels. > When is Tim Traveller's video on the subject coming out? You’d think exploring the closed parts of the catacombs would be right up his alley (actually I would be surprised if he did not try, even though he might not want to put that on YouTube). They’ve been cracking up on trespassers recently but it still is fairly popular with the urban exploration crowd.
- surfingdino 2y ago
  > Paris is very complicated underground. Besides the quarries there are the sewers, catacombs, some underground lakes, reservoirs, etc. It is definitely a complicating factor when planning new metro tunnels. I wonder if the French are considering digging underneath all those obstacles? Seems to be the way London has gone with the Elizabeth Line. Although that may still be shallower than Paris' quarries and lakes.
  - _notreallyme_ 2y ago
    > I wonder if the French are considering digging underneath all those obstacles? The problem is the Seine phreatic zone, which starts usually between 15 to 25m below the surface. Some GRS galleries are actually completely inundated and others have a level of water that varies between the seasons. In order to have some metro going underneath the Seine river, they had to freeze it first. It is not an easy task, so there must be a real advantage to going under the Seine.
  - sofixa 2y ago
    > I wonder if the French are considering digging underneath all those obstacles Paris has been doing it for decades. All new lines in Paris (such as metro line 14, opened in 1998, RER E) have been dug by tunnel boring machines, and are at a depth below 20m. Same goes for all new lines outside of Paris proper, like most of the Grand Paris Express 200km+ new lines.
- tuetuopay 2y ago
  Tim-like pedantry corner: the quarries and the catacumbs are actually the same thing. Catacumbs are parts of the quarries that have been turned to ossuaries, and are reachable from the wider quarry network. > You’d think exploring the closed parts of the catacombs would be right up his alley I'm not that sure, since he does not want to do illegal stuff (like for the belgian test track where the factory is now closed to the public). As for visiting those parts legally, well, I'm only aware of a few instances where there has been the media granted access. But it was more for documentaries about how the police works down there, not for a general history lesson. Both the police nor the IGC (the french administration managing the quarries) will bother with Tim sadly. So yes it'd be up his alley if he could do it legally. > They’ve been cracking up on trespassers recently It's actually the opposite. There's a constant cat-and-mouse game going on, and they're switching strategies recently, which I could experience first-hand. Current strategy is about prevention because they know they cannot prevent people from getting down there, so they're emphasizing safety and not hurting yourself because they "don't want to get woken up at 9AM a sunday morning because someone got lost".
  - kergonath 2y ago
    > Tim-like pedantry corner: the quarries and the catacumbs are actually the same thing. Catacumbs are parts of the quarries that have been turned to ossuaries, and are reachable from the wider quarry network. Fair enough. It’s still useful to distinguish them because they evoke different things. Also, aren’t the bits we can visit physically separated from the broader quarry network due to cave-ins? > I'm not that sure, since he does not want to do illegal stuff He certainly used to do this sort of things (and I did not check recently but in the past he posted some videos filmed in places where he was not allowed to be). There are places that are normally closed off but that can be open occasionally like during the heritage days. At least one quarry, the Montsouris reservoir, and I think parts of the old sewers as well. Those are already quite cool and interesting. > It's actually the opposite. There's a constant cat-and-mouse game going on, and they're switching strategies recently, which I could experience first-hand. There’s always a bit of both. I don’t have a recent first hand experience, it’s just a mate who works with the Parisian fire brigade. There are near misses regularly, though rarely as bad as the teenagers who got lost for 3 days a couple of years ago. > they're emphasizing safety and not hurting yourself because they "don't want to get woken up at 9AM a sunday morning because someone got lost". Makes sense. Going on a rescue mission before the morning coffee is just not done :)
tuetuopay 2y ago
I'll reply only on the second point because that's a topic I know (I happen to wander quite often in those quarries). And no, there is no mushroom production anymore in the quarries. The paris area is too crowded now, and for economies of scale, existing quarries are too hard to use, and will use old quarries further away (but not as old as the "catacumbs" to have larger tunnels easier to work in). Also, what's often called the catacumbs are quarries dating back to the middle ages, and thus are narrow, turny, wet, etc. Just a pain to work in. Oh, and don't forget the dwellers that like to go down there, and would be sure to spoil all the crops.

kergonath 2y ago

> Is Paris Metro so shallow because of the quarries? The Paris metro is a mixture of deep, subsurface, and surface tracks. There are a lot of shallow tunnels mostly because cut-and-cover was easier and cheaper than digging deep underground. Paris is very complicated underground. Besides the quarries there are the sewers, catacombs, some underground lakes, reservoirs, etc. It is definitely a complicating factor when planning new metro tunnels. > When is Tim Traveller's video on the subject coming out? You’d think exploring the closed parts of the catacombs would be right up his alley (actually I would be surprised if he did not try, even though he might not want to put that on YouTube). They’ve been cracking up on trespassers recently but it still is fairly popular with the urban exploration crowd.

surfingdino 2y ago
> Paris is very complicated underground. Besides the quarries there are the sewers, catacombs, some underground lakes, reservoirs, etc. It is definitely a complicating factor when planning new metro tunnels. I wonder if the French are considering digging underneath all those obstacles? Seems to be the way London has gone with the Elizabeth Line. Although that may still be shallower than Paris' quarries and lakes.
- _notreallyme_ 2y ago
  > I wonder if the French are considering digging underneath all those obstacles? The problem is the Seine phreatic zone, which starts usually between 15 to 25m below the surface. Some GRS galleries are actually completely inundated and others have a level of water that varies between the seasons. In order to have some metro going underneath the Seine river, they had to freeze it first. It is not an easy task, so there must be a real advantage to going under the Seine.
- sofixa 2y ago
  > I wonder if the French are considering digging underneath all those obstacles Paris has been doing it for decades. All new lines in Paris (such as metro line 14, opened in 1998, RER E) have been dug by tunnel boring machines, and are at a depth below 20m. Same goes for all new lines outside of Paris proper, like most of the Grand Paris Express 200km+ new lines.
tuetuopay 2y ago
Tim-like pedantry corner: the quarries and the catacumbs are actually the same thing. Catacumbs are parts of the quarries that have been turned to ossuaries, and are reachable from the wider quarry network. > You’d think exploring the closed parts of the catacombs would be right up his alley I'm not that sure, since he does not want to do illegal stuff (like for the belgian test track where the factory is now closed to the public). As for visiting those parts legally, well, I'm only aware of a few instances where there has been the media granted access. But it was more for documentaries about how the police works down there, not for a general history lesson. Both the police nor the IGC (the french administration managing the quarries) will bother with Tim sadly. So yes it'd be up his alley if he could do it legally. > They’ve been cracking up on trespassers recently It's actually the opposite. There's a constant cat-and-mouse game going on, and they're switching strategies recently, which I could experience first-hand. Current strategy is about prevention because they know they cannot prevent people from getting down there, so they're emphasizing safety and not hurting yourself because they "don't want to get woken up at 9AM a sunday morning because someone got lost".
- kergonath 2y ago
  > Tim-like pedantry corner: the quarries and the catacumbs are actually the same thing. Catacumbs are parts of the quarries that have been turned to ossuaries, and are reachable from the wider quarry network. Fair enough. It’s still useful to distinguish them because they evoke different things. Also, aren’t the bits we can visit physically separated from the broader quarry network due to cave-ins? > I'm not that sure, since he does not want to do illegal stuff He certainly used to do this sort of things (and I did not check recently but in the past he posted some videos filmed in places where he was not allowed to be). There are places that are normally closed off but that can be open occasionally like during the heritage days. At least one quarry, the Montsouris reservoir, and I think parts of the old sewers as well. Those are already quite cool and interesting. > It's actually the opposite. There's a constant cat-and-mouse game going on, and they're switching strategies recently, which I could experience first-hand. There’s always a bit of both. I don’t have a recent first hand experience, it’s just a mate who works with the Parisian fire brigade. There are near misses regularly, though rarely as bad as the teenagers who got lost for 3 days a couple of years ago. > they're emphasizing safety and not hurting yourself because they "don't want to get woken up at 9AM a sunday morning because someone got lost". Makes sense. Going on a rescue mission before the morning coffee is just not done :)

tuetuopay 2y ago

I'll reply only on the second point because that's a topic I know (I happen to wander quite often in those quarries). And no, there is no mushroom production anymore in the quarries. The paris area is too crowded now, and for economies of scale, existing quarries are too hard to use, and will use old quarries further away (but not as old as the "catacumbs" to have larger tunnels easier to work in). Also, what's often called the catacumbs are quarries dating back to the middle ages, and thus are narrow, turny, wet, etc. Just a pain to work in. Oh, and don't forget the dwellers that like to go down there, and would be sure to spoil all the crops.