6 ms·

Amazing read, much longer than I generally get hooked into. I am astonished that "Grouting" (A term i find like many in the engineering word makes a possibly q

by verelo 10y ago

Amazing read, much longer than I generally get hooked into. I am astonished that "Grouting" (A term i find like many in the engineering word makes a possibly questionable practice sound like a good idea) is a functional, let alone acceptable solution, I can only begin to imagine what the ground under that dam must look like after the last 20+ years of concrete being poured into it.

21 10y ago
One of the first steps in many building foundations is injecting concrete into the soil, typically in the form of pillars. Desperate times probably call for desperate solutions in this case.
- verelo 10y ago
  Interesting, is there any work done to first evacuate the area of soil or is it simply pushed out of the way using pressure from the concrete?
  - 21 10y ago
    Don't know, I guess it depends on the depth, for small buildings you just hammer the concrete pillar in - https://www.youtube.com/watch?v=VkXTLAxGKxA https://www.youtube.com/watch?v=VkXTLAxGKxA I'm surprised you never witnessed it, I've seen this at least 3-4 times. Probably because nowadays constructions sites have big opaque fences around them.
    - verelo 10y ago
      I recall my dad talking about something similar regarding the reconstruction of a building where he worked after and earthquake. I suspect I've heard it and passed it off as general construction noise, but not seen it due to the fences you referenced...interesting!
    - lobster_johnson 10y ago
      I've seen those, but always assumed they were driving steel beams into the earth. I'm surprised that concrete can be manhandled that way without being smashed into pieces.
      - abduhl 10y ago
        Driving concrete piling has generally been abandoned in USA/Canada/Western Europe due to the propensity of concrete to crack in tension during pile driving operations. Driven pile is typically steel now in most construction you will see unless you live in a place where concrete is extremely cheap compared to steel.
        lobster_johnson 10y ago
        In that case what I've observed was probably steel after all. Thanks.
        Someone 10y ago
        Wouldn't that be to crack in compression? Also, I don't see concrete piles being abandoned at all. Part of the reason may be that, where I live, many poles now are drilled, pressed or vibrated into the ground to decrease noise and potential impact on surrounding buildings. Thats is possible because there is no bedrock to build on where I live, so poles often go down easily for the first meters; I have seen wooden poles sink in five meters or so under their own weight. Traditional piling into the ground still is used, too. If necessary, a protective head cover on the pole (made from wood or, nowadays, plastic) softens the blows a bit, protecting the concrete from damage.
        abduhl 10y ago
        No, tension is what I meant. Imagine the pile hammer hitting the top of the pile. This impulse is transmitted down the length of the pile at the speed of sound as a wave. There exists a point where the wave gets to the end of the pile (this is at the pile tip) and the compression front attempts to continue which results in tension (eg - the pile tip is dragging itself forward with the energy). This is mostly seen with soft soils where end reaction is not sufficient to provide a hard "stop" on the pile. For hard ground, the opposite can occur where the driving energy reflects at the pile tip. This can result in huge compressive forces that crush (not crack) the concrete due to the two compressive waves (one new wave from the next hammer strike and the reflected wave from the previous hammer strike) stacking due to superposition. The reason that this failure mechanism wasn't noted by me is that steel piles suffer the same issue, so it is not a good reason to use steel over concrete piling. As you note, the solution to both issues is the use of a shoe and control of the hammer stroke. I should have been more clear, I guess. Driven concrete pile is not used in the USA/Canada in my experience. When deep concrete foundations are used they are typically drilled in, for the reasons cited above. There are obviously times when concrete piles are cheaper and will get the job done even with the risks above. This is most likely for smaller buildings where loadings are relatively light and pile lengths are therefore short.
    - abduhl 10y ago
      This is not grouting. This is driving concrete piles. Grouting refers to multiple things when talking about foundations or underground work but here are some examples: Jet grouting - high pressure water/grout/air is used to displace and mix the soil and grout to make a soilcrete Compensation grouting - grout is injected under pressure into the soil in order to displace/heave the ground to counteract previous settlement Cutoff grouting - grout is injected into the ground in order to cut off ground water What they're doing at the dam appears to be backfill grouting where they are injecting grout from within the dam underneath it trying to cut off the seepage path of the voids that have formed. This appears to be because they've built the dam on a soluble rock and so voids are constantly created which allow flow paths. They must find the voids and fill them with grout. This is a never ending process until all rock is replaced with grout.
      - quickben 10y ago
        But, how can they do this forever? They can't encase most of the reservoir in concrete?
  - deleted 10y ago
    [deleted]
- TazeTSchnitzel 10y ago
  When I looked up "grouting" on Wikipedia, I learned it's a process most dams use. But presumably only once.
rsync 10y ago
"Amazing read, much longer than I generally get hooked into." Please, please subscribe to the New Yorker in some fashion ... I personally subscribe to the kindle version which is a very useful and workable format. The New Yorker[1] regularly has very, very good long form articles that have deepened my understanding of what I consider to be very important issues. Off the top of my head, I can think of three such articles that stick out - their long treatment of the deepwater horizon accident and the chemical dispersants that were used in the cleanup, their decade-after-the-fact retrospective article on Gore vs. Bush, and a more recent article on the police officer who shot Michael Brown in Ferguson, MO. [1] Also the London Review of Books which is excellent for long form current events articles. Also book reviews.
- verelo 10y ago
  I often find when I do get lost in an article, it's common to be something from the New Yorker. The articles are very well written and often explore the story in a way that is factual and creative that I really enjoy. Reading "Precedent and Prologue" (Gore V's bush supreme court article) I got so interested in the judicial activism concept and ended up lost on Wikipedia for a few hours bouncing around related articles. The exact same thing happened to me with this Mosul Dam article, when I saw myself reading about Gaddafi I realized I had gone so far down the rabbit hole that the topics I was now reading about were only vaguely related. All said and done, it's a good point i really should become a paid subscriber, thanks for suggesting it!
  - nyolfen 10y ago
    it's gotten a lot of buzz lately, including on HN, but if you're interested in going down the gaddafi hole a bit further i'd recommend the recent adam curtis film, hypernormalisation. his films tend to be a bit like getting lost in a wikipedia hole in their own right, though.
    - emp_zealoth 10y ago
      Seconded Then watch Only The Dead (see the end of a war) by an australian bloke Good luck sleeping afterwards
DonHopkins 10y ago
Maybe it looks something like gargantuan concrete anthill art. https://www.youtube.com/watch?v=IGJ2jMZ-gaI https://www.youtube.com/watch?v=IGJ2jMZ-gaI

by verelo 10y ago

21 10y ago

One of the first steps in many building foundations is injecting concrete into the soil, typically in the form of pillars. Desperate times probably call for desperate solutions in this case.

verelo 10y ago
Interesting, is there any work done to first evacuate the area of soil or is it simply pushed out of the way using pressure from the concrete?
- 21 10y ago
  Don't know, I guess it depends on the depth, for small buildings you just hammer the concrete pillar in - https://www.youtube.com/watch?v=VkXTLAxGKxA https://www.youtube.com/watch?v=VkXTLAxGKxA I'm surprised you never witnessed it, I've seen this at least 3-4 times. Probably because nowadays constructions sites have big opaque fences around them.
  - verelo 10y ago
    I recall my dad talking about something similar regarding the reconstruction of a building where he worked after and earthquake. I suspect I've heard it and passed it off as general construction noise, but not seen it due to the fences you referenced...interesting!
  - lobster_johnson 10y ago
    I've seen those, but always assumed they were driving steel beams into the earth. I'm surprised that concrete can be manhandled that way without being smashed into pieces.
    - abduhl 10y ago
      Driving concrete piling has generally been abandoned in USA/Canada/Western Europe due to the propensity of concrete to crack in tension during pile driving operations. Driven pile is typically steel now in most construction you will see unless you live in a place where concrete is extremely cheap compared to steel.
      - lobster_johnson 10y ago
        In that case what I've observed was probably steel after all. Thanks.
      - Someone 10y ago
        Wouldn't that be to crack in compression? Also, I don't see concrete piles being abandoned at all. Part of the reason may be that, where I live, many poles now are drilled, pressed or vibrated into the ground to decrease noise and potential impact on surrounding buildings. Thats is possible because there is no bedrock to build on where I live, so poles often go down easily for the first meters; I have seen wooden poles sink in five meters or so under their own weight. Traditional piling into the ground still is used, too. If necessary, a protective head cover on the pole (made from wood or, nowadays, plastic) softens the blows a bit, protecting the concrete from damage.
        abduhl 10y ago
        No, tension is what I meant. Imagine the pile hammer hitting the top of the pile. This impulse is transmitted down the length of the pile at the speed of sound as a wave. There exists a point where the wave gets to the end of the pile (this is at the pile tip) and the compression front attempts to continue which results in tension (eg - the pile tip is dragging itself forward with the energy). This is mostly seen with soft soils where end reaction is not sufficient to provide a hard "stop" on the pile. For hard ground, the opposite can occur where the driving energy reflects at the pile tip. This can result in huge compressive forces that crush (not crack) the concrete due to the two compressive waves (one new wave from the next hammer strike and the reflected wave from the previous hammer strike) stacking due to superposition. The reason that this failure mechanism wasn't noted by me is that steel piles suffer the same issue, so it is not a good reason to use steel over concrete piling. As you note, the solution to both issues is the use of a shoe and control of the hammer stroke. I should have been more clear, I guess. Driven concrete pile is not used in the USA/Canada in my experience. When deep concrete foundations are used they are typically drilled in, for the reasons cited above. There are obviously times when concrete piles are cheaper and will get the job done even with the risks above. This is most likely for smaller buildings where loadings are relatively light and pile lengths are therefore short.
  - abduhl 10y ago
    This is not grouting. This is driving concrete piles. Grouting refers to multiple things when talking about foundations or underground work but here are some examples: Jet grouting - high pressure water/grout/air is used to displace and mix the soil and grout to make a soilcrete Compensation grouting - grout is injected under pressure into the soil in order to displace/heave the ground to counteract previous settlement Cutoff grouting - grout is injected into the ground in order to cut off ground water What they're doing at the dam appears to be backfill grouting where they are injecting grout from within the dam underneath it trying to cut off the seepage path of the voids that have formed. This appears to be because they've built the dam on a soluble rock and so voids are constantly created which allow flow paths. They must find the voids and fill them with grout. This is a never ending process until all rock is replaced with grout.
    - quickben 10y ago
      But, how can they do this forever? They can't encase most of the reservoir in concrete?
- deleted 10y ago
  [deleted]
TazeTSchnitzel 10y ago
When I looked up "grouting" on Wikipedia, I learned it's a process most dams use. But presumably only once.

rsync 10y ago

"Amazing read, much longer than I generally get hooked into." Please, please subscribe to the New Yorker in some fashion ... I personally subscribe to the kindle version which is a very useful and workable format. The New Yorker[1] regularly has very, very good long form articles that have deepened my understanding of what I consider to be very important issues. Off the top of my head, I can think of three such articles that stick out - their long treatment of the deepwater horizon accident and the chemical dispersants that were used in the cleanup, their decade-after-the-fact retrospective article on Gore vs. Bush, and a more recent article on the police officer who shot Michael Brown in Ferguson, MO. [1] Also the London Review of Books which is excellent for long form current events articles. Also book reviews.

verelo 10y ago
I often find when I do get lost in an article, it's common to be something from the New Yorker. The articles are very well written and often explore the story in a way that is factual and creative that I really enjoy. Reading "Precedent and Prologue" (Gore V's bush supreme court article) I got so interested in the judicial activism concept and ended up lost on Wikipedia for a few hours bouncing around related articles. The exact same thing happened to me with this Mosul Dam article, when I saw myself reading about Gaddafi I realized I had gone so far down the rabbit hole that the topics I was now reading about were only vaguely related. All said and done, it's a good point i really should become a paid subscriber, thanks for suggesting it!
- nyolfen 10y ago
  it's gotten a lot of buzz lately, including on HN, but if you're interested in going down the gaddafi hole a bit further i'd recommend the recent adam curtis film, hypernormalisation. his films tend to be a bit like getting lost in a wikipedia hole in their own right, though.
  - emp_zealoth 10y ago
    Seconded Then watch Only The Dead (see the end of a war) by an australian bloke Good luck sleeping afterwards

DonHopkins 10y ago

Maybe it looks something like gargantuan concrete anthill art. https://www.youtube.com/watch?v=IGJ2jMZ-gaI https://www.youtube.com/watch?v=IGJ2jMZ-gaI