3 ms·

To eliminate some of the raised issues, particularly around the forces acting during the installation, the conduit could be assembled from sections, in the guis

To eliminate some of the raised issues, particularly around the forces acting during the installation, the conduit could be assembled from sections, in the guise of HVAC ventilation shafts[0]. With that said, I won't add any further speculation since mechanical/materials engineering is really not my area of expertise. Someone knowledgeable could provide insight on: what material (steel?) is suitable for such a task and what are processes for watertight bonding performed underwater (welding?). 0: https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-1-768x337.jpg https://bigreddog.com/wp-content/uploads/2016/02/Ductwork-1-...

eesmith 8y ago
There is no need for a materials engineer. We can look to existing structures which hold water to get an idea. Above ground pools use 1/8" steel for about 1-1.5 meters of water depth. (Eg, https://www.answers.com/Q/How_thick_is_a_swimming_pool https://www.answers.com/Q/How_thick_is_a_swimming_pool ) Pressure is linear with depth, so 6 meters would require about 1/2" of steel. HVAC ducts like you pointed to are about 1/40". (Based on numbers I see at https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/Chapter%206_Duct%20Systems.pdf https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/... ).
- simon_acca 8y ago
  I just pointed at hvac ducts to illustrate the kind of tech I was referring to (pipes assembled from small sections), wasn’t suggesting that actual hvac pipes should be used
  - eesmith 8y ago
    Ahh, I see. I misunderstood. Your model, I think, is that the divers would lay at least 1km of 1/2" thick steel pipe, from the far end backwards (since otherwise there's no way to get the segments to the end). Call it 1cm for easy of calculation. Steel is 8g/cubic centimeter. Assuming the divers can carry 20kg (which seems large), each segment is at most 25 cm long. That's at least 4,000 segments, each to be welded. Assuming it takes 5 minutes per weld, that's 13 days of non-stop work. And I am assuming that the welding equipment doesn't need to be moved in. As Johnny555 pointed out elsewhere in these threads, the divers are having problems putting in a communications cable, which is much smaller and more flexible.
    - simon_acca 8y ago
      Thanks for doing the math, looks plausible to me. Just for the argument sake, since there seem to be logistical problems (hey, Hanoi is not that far away, right?) to the whole solution: you could carry out several non-adjacent welds in parallel and then join these segments together, that would speed things up. The data cable seem to have water damage problems, something that would not be a concern here it seems.
      - eesmith 8y ago
        How do the divers get to the non-adjacent welds if the pipe blocks their way? How are they supplied? Why should we assume that the require equipment won't also suffer from water damage? Eg, "around small passages" might mean the cable scraped against the wall, causing water to leak in. BTW, it seems the critical section is under 5 meters of water, not 6 as I thought, and is 70cm across. And it seems one of the divers just died. If that's an indication of the mortality rate, then imagine how many might die building a tube.

eesmith 8y ago

There is no need for a materials engineer. We can look to existing structures which hold water to get an idea. Above ground pools use 1/8" steel for about 1-1.5 meters of water depth. (Eg, https://www.answers.com/Q/How_thick_is_a_swimming_pool https://www.answers.com/Q/How_thick_is_a_swimming_pool ) Pressure is linear with depth, so 6 meters would require about 1/2" of steel. HVAC ducts like you pointed to are about 1/40". (Based on numbers I see at https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/Chapter%206_Duct%20Systems.pdf https://www2.iccsafe.org/states/newyorkcity/Mechanical/PDFs/... ).

simon_acca 8y ago
I just pointed at hvac ducts to illustrate the kind of tech I was referring to (pipes assembled from small sections), wasn’t suggesting that actual hvac pipes should be used
- eesmith 8y ago
  Ahh, I see. I misunderstood. Your model, I think, is that the divers would lay at least 1km of 1/2" thick steel pipe, from the far end backwards (since otherwise there's no way to get the segments to the end). Call it 1cm for easy of calculation. Steel is 8g/cubic centimeter. Assuming the divers can carry 20kg (which seems large), each segment is at most 25 cm long. That's at least 4,000 segments, each to be welded. Assuming it takes 5 minutes per weld, that's 13 days of non-stop work. And I am assuming that the welding equipment doesn't need to be moved in. As Johnny555 pointed out elsewhere in these threads, the divers are having problems putting in a communications cable, which is much smaller and more flexible.
  - simon_acca 8y ago
    Thanks for doing the math, looks plausible to me. Just for the argument sake, since there seem to be logistical problems (hey, Hanoi is not that far away, right?) to the whole solution: you could carry out several non-adjacent welds in parallel and then join these segments together, that would speed things up. The data cable seem to have water damage problems, something that would not be a concern here it seems.
    - eesmith 8y ago
      How do the divers get to the non-adjacent welds if the pipe blocks their way? How are they supplied? Why should we assume that the require equipment won't also suffer from water damage? Eg, "around small passages" might mean the cable scraped against the wall, causing water to leak in. BTW, it seems the critical section is under 5 meters of water, not 6 as I thought, and is 70cm across. And it seems one of the divers just died. If that's an indication of the mortality rate, then imagine how many might die building a tube.