A bigger problem than ISIS: The Mosul Dam is failing • Hacker News Board

Re: A bigger problem than ISIS: The Mosul Dam is failing

#31

Post by TazeTSchnitzel » Tue, Dec 27, 2016, 4:55 AM UTC

21 wrote: post #8

verelo wrote: post #2

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.

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.

When I looked up "grouting" on Wikipedia, I learned it's a process most dams use.

But presumably only once.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#32

Post by verelo » Tue, Dec 27, 2016, 5:02 AM UTC

rsync wrote: post #26

verelo wrote: post #2

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.

"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 artic…

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!

Re: A bigger problem than ISIS: The Mosul Dam is failing

#33

Post by abecedarius » Tue, Dec 27, 2016, 5:03 AM UTC

logicallee wrote: post #25

unethical_ban wrote: post #6

The caption of a picture says the reservoir holds 11 billion cubic FEET, but the article earlier says METERS. That's a magnitude of difference.

I'm curious, were you calculating or using (or thinking about, had some train of thought about) this information or did you just happen to notice the mixed units? I mean because I can't picture either one or ten billion cubic feet of water so it's just a very large number to me and I wouldn't notice that difference.

For me it helps to think about the cube root of the figure -- a billion cubic feet is 10^9, meaning a cube 10^3 feet on a side. About a fifth of a mile.

A meter is over 3 feet, so a cubic meter is over 3^3 or 27 cubic feet. You can ask google for a precise value: https://www.google.com/search?q=cubic+meter+in+cubic+feet And 10^3 meters on a side would be a kilometer.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#34

Post by verelo » Tue, Dec 27, 2016, 5:04 AM UTC

21 wrote: post #12

verelo wrote: post #9

Earlier quoted context omitted.

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?

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 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.

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!

Re: A bigger problem than ISIS: The Mosul Dam is failing

#35

Post by dajohnson89 » Tue, Dec 27, 2016, 5:09 AM UTC

Sorry if this is a dumb question. TBH I didn't rtfa. But if the dam needs a constant infusion of concrete in order to not fail, why wasn't anything done to evacuate the area and gracefully (sic) fail the dam in the first place?

Re: A bigger problem than ISIS: The Mosul Dam is failing

#36

Post by lobster_johnson » Tue, Dec 27, 2016, 5:15 AM UTC

rsync wrote: post #26

verelo wrote: post #2

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.

"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 artic…

The New York Review of Books is also wonderful. I prefer it to the LRB, though they share a bunch of contributors, and they're both great.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#37

Post by lobster_johnson » Tue, Dec 27, 2016, 5:19 AM UTC

21 wrote: post #12

verelo wrote: post #9

Earlier quoted context omitted.

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?

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 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.

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.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#38

Post by ChrisGranger » Tue, Dec 27, 2016, 5:23 AM UTC

StavrosK wrote: post #29

unethical_ban wrote: post #6

The caption of a picture says the reservoir holds 11 billion cubic FEET, but the article earlier says METERS. That's a magnitude of difference.

Actually closer to two, 1m3 = 74ft3.

One cubic meter is 35 cubic feet, not 74.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#39

Post by abduhl » Tue, Dec 27, 2016, 5:26 AM UTC

21 wrote: post #12

verelo wrote: post #9

Earlier quoted context omitted.

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?

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 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.

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.

Re: A bigger problem than ISIS: The Mosul Dam is failing

#40

Post by abduhl » Tue, Dec 27, 2016, 5:29 AM UTC

lobster_johnson wrote: post #37

21 wrote: post #12

Earlier quoted context omitted.

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 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.

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.

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.