> 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?
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?
https://en.wikipedia.org/wiki/Staufen_im_Breisgau#Geothermal...
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
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.
Fascinating, thanks!
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.
> What the heck?