4 ms·

> in most cases, you can just keep driving downward until you do! I feel that the cases in which that technique doesn't work are stories to be told. Do you jus

> in most cases, you can just keep driving downward until you do! I feel that the cases in which that technique doesn't work are stories to be told. Do you just keep driving downward for a very long time? How long?

0xTJ 2y ago
Satan, far below some very deep, soft, and slippery soil where an overpass needs to go: > What the heck?
bell-cot 2y ago
IANAE (No An Engineer), but I think he mentions both the issues of piles wandering off-course, and of unanticipated piling problems causing major budget & scheduling issues. From a structural PoV, an extremely long piling in soft-ish soil will start having problems with lateral deflection - which it is too thin (relative to length) to resist. Then there's the case of "we think we finally hit bedrock...but what if it's just a big boulder?". I can imagine cases of pilings running into large underground caverns, or penetrating strata containing water / gas / petroleum under pressure. Edit: From a quick search... In some locations, bedrock may not start until >1000' below the surface. And here's a very quick & simple intro to the fact that "bedrock starts at depth D" is usually too simplistic: https://education.nationalgeographic.org/resource/bedrock/ https://education.nationalgeographic.org/resource/bedrock/
- adolph 2y ago
  > I can imagine cases of pilings running into large underground caverns Example being the Lake Peigneur disaster. https://64parishes.org/entry/lake-peigneur-drilling-accident https://64parishes.org/entry/lake-peigneur-drilling-accident On the morning of November 20, 1980, the crew drilling near the salt mining operations reported that the tip of their drill shaft was stuck. After the crew removed the tip, they heard strange noises and abandoned the platform in the nick of time. A giant mud crater began sucking down barges, rigs, and almost some fishermen who escaped with moments to spare.
  - trilbyglens 2y ago
    [flagged]
    - adolph 2y ago
      In 1980 south Louisiana, “those schmucks” were likely staunch Democrats, following their forebears since the Republican association with reconstruction efforts after the American civil war.
      - adolph 2y ago
        Goodness, so much hate of honest history. Louisiana is where “vote for the crook, it’s important” actually happened. https://en.wikipedia.org/wiki/1991_Louisiana_gubernatorial_election https://en.wikipedia.org/wiki/1991_Louisiana_gubernatorial_e...
    - kortilla 2y ago
      That’s at will employment. Works exactly the same fucking way in California where “those schmucks” certainly aren’t voting R.
- beerandt 2y ago
  >Then there's the case of "we think we finally hit bedrock...but what if it's just a big boulder?" Doesn't matter. There's two types of pile support: noncohesive and cohesive. Which can be thought of as end (bearing) resistance and side (friction) resistance. Most people only think of end resistance. Most end resistance piles aren't driven to bedrock or even a boulder, but a strata of soil with sufficient strength. Usually a layer of sand under silt or clay, but a boulder could do it. Here's the catch- if it's a one-off, then adjacent piles won't hit it, and you'll see the anomaly. Mitigation may or may not be required. If it's not, then you've hit a strong (noncohesive) layer of boulders. Either way- it goes back to the point: each pile is resistance tested. And you know now not only the insitu soil strength, but also that of each layer to reach that depth. Also side note- the act of driving and then post-drive settling both build addl strength. Eg, The force used to drive the pile, applied a few months later, usually won't be sufficient to drive it any further.
moffkalast 2y ago
https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole
lqet 2y ago
Well, whatever you do, do not perforate an anhydrite layer! https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal_drilling_controversy https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...
- orls 2y ago
  This is fascinating, thankyou!
- pixl97 2y ago
  Another one to watch out for is mud diapirs. In coastal deltas where thousands of feet of infill has occurred over time the interaction between hydrocarbon formation and organic silts can create mud volcanoes. https://www.researchgate.net/figure/Comparison-of-signatures-of-mud-and-salt-diapirism-A-Mud-diapirism-indicates-a-zone-of_fig7_285870003 https://www.researchgate.net/figure/Comparison-of-signatures... These can be anywhere things that shoot liquid mud out of the ground to areas of very deep low seismic velocities where you could drive a pile thousands of feet to the bottom of hell and barely get any resistance. Much the same, one should be careful when drilling into mud layers https://en.wikipedia.org/wiki/Sidoarjo_mud_flow https://en.wikipedia.org/wiki/Sidoarjo_mud_flow
- crazygringo 2y ago
  Wow. I knew drilling could cause land to sink. I never imagined it could cause land to rise. Fascinating, thanks!
- Terr_ 2y ago
  Also don't accidentally let a lake--and the boats in it--start filling your tunnels through salt. https://en.wikipedia.org/wiki/Lake_Peigneur https://en.wikipedia.org/wiki/Lake_Peigneur
  - pas 2y ago
    > Days after the disaster, once the water pressure equalized, nine of the eleven sunken barges popped out of the whirlpool and refloated on the lake's surface. wow. > there were no human deaths, three dogs were reported killed. All 55 employees in the mine at the time of the accident escaped omF...g the mine was active!? and folks were just drilling on top of it!??? huh. good old 1980s.

0xTJ 2y ago

Satan, far below some very deep, soft, and slippery soil where an overpass needs to go: > What the heck?

bell-cot 2y ago

IANAE (No An Engineer), but I think he mentions both the issues of piles wandering off-course, and of unanticipated piling problems causing major budget & scheduling issues. From a structural PoV, an extremely long piling in soft-ish soil will start having problems with lateral deflection - which it is too thin (relative to length) to resist. Then there's the case of "we think we finally hit bedrock...but what if it's just a big boulder?". I can imagine cases of pilings running into large underground caverns, or penetrating strata containing water / gas / petroleum under pressure. Edit: From a quick search... In some locations, bedrock may not start until >1000' below the surface. And here's a very quick & simple intro to the fact that "bedrock starts at depth D" is usually too simplistic: https://education.nationalgeographic.org/resource/bedrock/ https://education.nationalgeographic.org/resource/bedrock/

adolph 2y ago
> I can imagine cases of pilings running into large underground caverns Example being the Lake Peigneur disaster. https://64parishes.org/entry/lake-peigneur-drilling-accident https://64parishes.org/entry/lake-peigneur-drilling-accident On the morning of November 20, 1980, the crew drilling near the salt mining operations reported that the tip of their drill shaft was stuck. After the crew removed the tip, they heard strange noises and abandoned the platform in the nick of time. A giant mud crater began sucking down barges, rigs, and almost some fishermen who escaped with moments to spare.
- trilbyglens 2y ago
  [flagged]
  - adolph 2y ago
    In 1980 south Louisiana, “those schmucks” were likely staunch Democrats, following their forebears since the Republican association with reconstruction efforts after the American civil war.
    - adolph 2y ago
      Goodness, so much hate of honest history. Louisiana is where “vote for the crook, it’s important” actually happened. https://en.wikipedia.org/wiki/1991_Louisiana_gubernatorial_election https://en.wikipedia.org/wiki/1991_Louisiana_gubernatorial_e...
  - kortilla 2y ago
    That’s at will employment. Works exactly the same fucking way in California where “those schmucks” certainly aren’t voting R.
beerandt 2y ago
>Then there's the case of "we think we finally hit bedrock...but what if it's just a big boulder?" Doesn't matter. There's two types of pile support: noncohesive and cohesive. Which can be thought of as end (bearing) resistance and side (friction) resistance. Most people only think of end resistance. Most end resistance piles aren't driven to bedrock or even a boulder, but a strata of soil with sufficient strength. Usually a layer of sand under silt or clay, but a boulder could do it. Here's the catch- if it's a one-off, then adjacent piles won't hit it, and you'll see the anomaly. Mitigation may or may not be required. If it's not, then you've hit a strong (noncohesive) layer of boulders. Either way- it goes back to the point: each pile is resistance tested. And you know now not only the insitu soil strength, but also that of each layer to reach that depth. Also side note- the act of driving and then post-drive settling both build addl strength. Eg, The force used to drive the pile, applied a few months later, usually won't be sufficient to drive it any further.

moffkalast 2y ago

https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole

lqet 2y ago

Well, whatever you do, do not perforate an anhydrite layer! https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal_drilling_controversy https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...

orls 2y ago
This is fascinating, thankyou!
pixl97 2y ago
Another one to watch out for is mud diapirs. In coastal deltas where thousands of feet of infill has occurred over time the interaction between hydrocarbon formation and organic silts can create mud volcanoes. https://www.researchgate.net/figure/Comparison-of-signatures-of-mud-and-salt-diapirism-A-Mud-diapirism-indicates-a-zone-of_fig7_285870003 https://www.researchgate.net/figure/Comparison-of-signatures... These can be anywhere things that shoot liquid mud out of the ground to areas of very deep low seismic velocities where you could drive a pile thousands of feet to the bottom of hell and barely get any resistance. Much the same, one should be careful when drilling into mud layers https://en.wikipedia.org/wiki/Sidoarjo_mud_flow https://en.wikipedia.org/wiki/Sidoarjo_mud_flow
crazygringo 2y ago
Wow. I knew drilling could cause land to sink. I never imagined it could cause land to rise. Fascinating, thanks!
Terr_ 2y ago
Also don't accidentally let a lake--and the boats in it--start filling your tunnels through salt. https://en.wikipedia.org/wiki/Lake_Peigneur https://en.wikipedia.org/wiki/Lake_Peigneur
- pas 2y ago
  > Days after the disaster, once the water pressure equalized, nine of the eleven sunken barges popped out of the whirlpool and refloated on the lake's surface. wow. > there were no human deaths, three dogs were reported killed. All 55 employees in the mine at the time of the accident escaped omF...g the mine was active!? and folks were just drilling on top of it!??? huh. good old 1980s.