Favorite bit:
The tagline of the Pile Driving Contractors Association is “A Driven Pile is a Tested Pile” because, just by installing them, you’ve verified that they can withstand a certain amount of force. After all, you had to overcome that force to get them in the ground. And if you’re not seeing enough resistance, in most cases, you can just keep driving downward until you do!
I can imagine that slow static loading could allow sinking whereas dynamic force would not. Soil liquification is a weird thing, analogous to silly putty where it can be soft when manipulated slowly but hard when impacted quickly.
Yeah, it also assume that the pile you're driving can be arbitrarily long and will last forever. They used to be made with trees, for which this is obviously false.
It depends. Fully soaked ground will actually preserve wooden piles (wood decay is aerobic and requires oxygen). This is why Venice and New Orleans are both built on them (sinking issues aside because they have other issues). The piles in both cases are quite stable because the ground is completely soaked. Where you run into issues is where water and air meet. I would imagine wooden piles in just water would have issues with shipworm (in appropriate venues). But the ones in fully soaked soil seem to last just fine.
I suspect, but don't have data on, that wooden piles may actually last longer in those exact circumstances due to galvanic issues with concrete and rebar or metal pilings.
When building fences, the ground-air interface is often where rot occurs, and there are products to protect that area:
* https://www.postsaver.com/en-gb/products/pro-sleeve-fence-po...
Any idea how well those stand up to lawn trimmers?
It looks like a layer of plastics, so I would expect not well. Though, the part you'd hit would be above the ground, so it might still protect pretty decently for all the below ground stuff. You might consider putting a small set of stones around it so that the trimmer cord hits those instead of the wrapped wood.
Stones could help with drainage and drying as well.
Parts of Amsterdam as well.
But they don't last forever, so a lot of them are being replaced at the moment. Expensive operation as they have to be replaced in-place, but Amsterdam canal front houses are prime real estate.
Not to mention that wooden piles were often treated with an absolutely massive amount of creosote, to the point that a number of timber pile treatment yards are superfund sites.
“the slow blade penetrates the shield“
Especially for trains. For one, they are much more susceptible to sinking, but also likely produce all kinds of resonance.
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?
Well, whatever you do, do not perforate an anhydrite layer!
https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...
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
wow.
omF...g the mine was active!? and folks were just drilling on top of it!???
huh. good old 1980s.
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...
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
This is fascinating, thankyou!
Wow. I knew drilling could cause land to sink. I never imagined it could cause land to rise.
Fascinating, thanks!
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/
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.
Example being the Lake Peigneur disaster.
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.
https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole
Satan, far below some very deep, soft, and slippery soil where an overpass needs to go:
Many have said similar about their code
What does this mean exactly?
works on my box
"if you’re not seeing enough resistance, in most cases, you can just keep driving downward until you do" -> "Many have said similar about their code" -> "works on my box"
How does this make sense or have any coherency?
User-side tests are the only tests that really matter.
Everything else you do is there just to reduce the odds of users tests catching anything. But you don't get any certainty before that step... that happens after your software is on production and people depend on it.
(Of course, that's a worldview that can be either very beneficial or incredibly harmful depending on what you are creating. It's not good to see it applied to bridges, but I believe the OP did it in jest.)
That's why we call it big test, not production.
Utilizing “Brute Force” as a testing and verification strategy.
Maybe it's a parallel to "if it runs, it works" :)
Unless you are talking about fancy dependent typing you might misunderstand the quip. Writing code does not test it.
Tested at the moment of installation != test valid 30 years later
how does that hold up to quake liquification?