4 ms·

> I was expecting Musk's company to improve the back end of the TBM. IMHO that doesn't even start to scratch the main problem that they gloss over or sometimes

> I was expecting Musk's company to improve the back end of the TBM. IMHO that doesn't even start to scratch the main problem that they gloss over or sometimes even appear to purposely ignore. The main problem with tunneling in urban areas is subsidence, and all the financial compensations that must be paid to those who see their property start to show structural problems due to the resulting differential settlement. I never saw this issue being addressed by either Musk's fanboys or any representative. Tunneling takes time not because of the amount of dirt that needs to be taken out but because even highly controlled tunneling operations can expect differential surface settlements in the order of inches. Musk didn't suddenly and single-handedly invented the concept of tunneling. People have been tunneling for quite a few decades and these problems are still hard to handle. Yet, somehow this issue is never addressed in these marketing blurbs.

yourapostasy 9y ago
It seems that the subsidence is because the tunnel does not reproduce the expansion-contraction characteristics of the spoil it replaces. A possible modernization is massively-dense conditions sampling along the proposed tunnel route, not just in the volume the tunnel replaces, but around it as well, possibly all the way up to the surface. Conditions I can think of off-hand are temperature, ambient moisture/humidity, drainage volume, and groundwater baseline versus historical. Set up the sampling as many years in advance as possible to establish good reference data. Then create hydraulically moveable tunnel rings that push against a static ring, to re-create the desired movement. Use machine learning to refine the model during the pre-construction sampling period, and to refine results during operational period. The sampling of the surrounding volume feeds into the machine learning datastream so the hydraulic movements can be anticipated and performed very slowly over time.
- semi-extrinsic 9y ago
  > Set up the sampling as many years in advance as possible to establish good reference data. Then create hydraulically moveable tunnel rings that push against a static ring, to re-create the desired movement. Use machine learning to refine the model during the pre-construction sampling period, and to refine results during operational period. Yeah, it's definitely going to be cheaper to just pay for subsidence. Not to mention that it's literally impossible to perform the kind of sampling you're talking about. It's basically the ultimate wet dream of the oil, gas and mining industries and they've poured trillions of dollars into developing subsurface sampling for over a century, with nowhere near the resolution you're thinking about.
rorykoehler 9y ago
I thought the depth and narrowness of the tunnels was to address this?
- geezerjay 9y ago
  > I thought the depth and narrowness of the tunnels was to address this? No, changing the stress field within the soil layers changes that. Digging a tunnel through soil causes a decompression that isn't balanced by either the tunneler or the supporting structure. That happens even if the tunnel is pre-grouted, which takes a considerable amount of time and money. Musk's team excels at marketing, but if you ask any civil engineer who has any knowledge of tunneling (the boring company) or railway systems (hyperloop) he'll be able to point out about a dozen basic and major technical and economical problems that they simply fail to address or even consider. The reason things are the way they are isn't due to a major conspiracy, or widespread stupidity. In fact, the only stupidity I see is in how these projects promise magical solutions to problems they even failed to identify adequately. I believe there are strong reasons why all these business pitches end with requests for investors to cough up cash to pay for the projects themselves, even though these million-dollar projects are proposed by a billionaire with a net worth of around 20 billion dollars.
  - hoopladler 9y ago
    Thanks for the post! I guess there are a few things that might make these projects less of an unmitigated disaster than your analysis suggests: 1. Musk is clearly working off the common delusion that 'getting in at the ground floor' is a good idea. In reality, innovators and groundbreakers typically go bankrupt. Investors who buy the bankrupt company are the ones who typically profit off the expensive research and development, without the associated risks. 2. If you consider similar examples, for instance, the English railway system - early investors losing money is by no means a bad thing. Even if 'getting in early' is bad business strategy, it's good for society in general if moonshots get funded, even if they never turn out to be profitable. 3. These projects, while obviously unsound and based on false premisses, will typically produce useful technology, knowledge, or techniques - that can later be taken up by governments (as in the case of railways) or private investors. So I mean, sure, these projects are stupid and will end in stupidity. But they're also a better (from a human perspective) use of investor capital than pretty much everything else it could be spent on - more Walmarts, Amazon surveillance devices, or oil exploration - even if those things are certainly safer bets in terms of profits.

yourapostasy 9y ago

It seems that the subsidence is because the tunnel does not reproduce the expansion-contraction characteristics of the spoil it replaces. A possible modernization is massively-dense conditions sampling along the proposed tunnel route, not just in the volume the tunnel replaces, but around it as well, possibly all the way up to the surface. Conditions I can think of off-hand are temperature, ambient moisture/humidity, drainage volume, and groundwater baseline versus historical. Set up the sampling as many years in advance as possible to establish good reference data. Then create hydraulically moveable tunnel rings that push against a static ring, to re-create the desired movement. Use machine learning to refine the model during the pre-construction sampling period, and to refine results during operational period. The sampling of the surrounding volume feeds into the machine learning datastream so the hydraulic movements can be anticipated and performed very slowly over time.

semi-extrinsic 9y ago
> Set up the sampling as many years in advance as possible to establish good reference data. Then create hydraulically moveable tunnel rings that push against a static ring, to re-create the desired movement. Use machine learning to refine the model during the pre-construction sampling period, and to refine results during operational period. Yeah, it's definitely going to be cheaper to just pay for subsidence. Not to mention that it's literally impossible to perform the kind of sampling you're talking about. It's basically the ultimate wet dream of the oil, gas and mining industries and they've poured trillions of dollars into developing subsurface sampling for over a century, with nowhere near the resolution you're thinking about.

rorykoehler 9y ago

I thought the depth and narrowness of the tunnels was to address this?

geezerjay 9y ago
> I thought the depth and narrowness of the tunnels was to address this? No, changing the stress field within the soil layers changes that. Digging a tunnel through soil causes a decompression that isn't balanced by either the tunneler or the supporting structure. That happens even if the tunnel is pre-grouted, which takes a considerable amount of time and money. Musk's team excels at marketing, but if you ask any civil engineer who has any knowledge of tunneling (the boring company) or railway systems (hyperloop) he'll be able to point out about a dozen basic and major technical and economical problems that they simply fail to address or even consider. The reason things are the way they are isn't due to a major conspiracy, or widespread stupidity. In fact, the only stupidity I see is in how these projects promise magical solutions to problems they even failed to identify adequately. I believe there are strong reasons why all these business pitches end with requests for investors to cough up cash to pay for the projects themselves, even though these million-dollar projects are proposed by a billionaire with a net worth of around 20 billion dollars.
- hoopladler 9y ago
  Thanks for the post! I guess there are a few things that might make these projects less of an unmitigated disaster than your analysis suggests: 1. Musk is clearly working off the common delusion that 'getting in at the ground floor' is a good idea. In reality, innovators and groundbreakers typically go bankrupt. Investors who buy the bankrupt company are the ones who typically profit off the expensive research and development, without the associated risks. 2. If you consider similar examples, for instance, the English railway system - early investors losing money is by no means a bad thing. Even if 'getting in early' is bad business strategy, it's good for society in general if moonshots get funded, even if they never turn out to be profitable. 3. These projects, while obviously unsound and based on false premisses, will typically produce useful technology, knowledge, or techniques - that can later be taken up by governments (as in the case of railways) or private investors. So I mean, sure, these projects are stupid and will end in stupidity. But they're also a better (from a human perspective) use of investor capital than pretty much everything else it could be spent on - more Walmarts, Amazon surveillance devices, or oil exploration - even if those things are certainly safer bets in terms of profits.