Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
(OP)
Hello.
I've tried to find an answer during hard internet search (without result). I hope you'll help me.
Input:
1.Pedestrian bridge
2. Soil conditions ( 1m of sand, 4-5m of expansive clay with high expansive strain, weathered rock - argillite),
3. Therefore - pile abutment (flood is common thing in this place, so clay will expand -> we need to go further to the rock)
Design process:
First idea - boring piles d=600-800mm was banned ( too expensive, uneducated workers (Eastern Europe) + too hard to control pile quality). Second idea - precast concrete driven piles (rectangular 350x350mm). But here we have a problem.
Rock layer have rather steep angle, so we can't guarantee reliability of pile's end bearing, because during driving pile's shoe can slip down and pile will go out of it's normal way.
Things may go like here (except welding joints, our pile is solid - one section)[Pile Design and Construction Practice, sixth ed., Tomlinson, Woodward].

Third idea - drive pile (rectangular) in pre-bored hole (d=400mm - bore 0.5-1m in rock) and then put a low-class concrete between pile and soil.
Or fourth idea - drive pile (rectangular) in pre-bored hole (d=300mm - bore 0.5-1m in rock). I'm afraid that in that case pile's end won't completely enter in rock or corners of pile's end will shear, but on the other hand rock is rather weathered.
And here is my question. Does anybody knows anything about such thing in practice (book, article)? Or some help in terminology, how this method called in world practice? Or maybe somebody can tell me about proper way to create a reliable contact between rock and pile.
Thank you.
I've tried to find an answer during hard internet search (without result). I hope you'll help me.
Input:
1.Pedestrian bridge
2. Soil conditions ( 1m of sand, 4-5m of expansive clay with high expansive strain, weathered rock - argillite),
3. Therefore - pile abutment (flood is common thing in this place, so clay will expand -> we need to go further to the rock)
Design process:
First idea - boring piles d=600-800mm was banned ( too expensive, uneducated workers (Eastern Europe) + too hard to control pile quality). Second idea - precast concrete driven piles (rectangular 350x350mm). But here we have a problem.
Rock layer have rather steep angle, so we can't guarantee reliability of pile's end bearing, because during driving pile's shoe can slip down and pile will go out of it's normal way.
Things may go like here (except welding joints, our pile is solid - one section)[Pile Design and Construction Practice, sixth ed., Tomlinson, Woodward].

Third idea - drive pile (rectangular) in pre-bored hole (d=400mm - bore 0.5-1m in rock) and then put a low-class concrete between pile and soil.
Or fourth idea - drive pile (rectangular) in pre-bored hole (d=300mm - bore 0.5-1m in rock). I'm afraid that in that case pile's end won't completely enter in rock or corners of pile's end will shear, but on the other hand rock is rather weathered.
And here is my question. Does anybody knows anything about such thing in practice (book, article)? Or some help in terminology, how this method called in world practice? Or maybe somebody can tell me about proper way to create a reliable contact between rock and pile.
Thank you.





RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
Why do you need to use 600-800mm dia? What are your loads/span? If it is a pedestrian bridge (i.e. not that heavily loaded) can you get away with 450-500mm dia bored in to rock. Substantially cheaper than 600-800mm dia. Also, if you have a good site engineer you can control the quality. If it is just a bridge then there cant be too many piles (depending on span etc)
How steep is the dip in your rock, do you have levels of top of rock to work out a gradient. IMHO, it would have to be very steep before you could consider the pile sliding down the top of rock? I have never encountered such a problem so maybe some who has can chime in.
If youre going to bore with of d=400mm and 1m into rock why not fill it full of concrete and it can be your pile!?
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
oldestguy, thank you for advice. I'll consider it.
EireChch , i've forgot to mention about seismic activity with design intensity 9.0 (MSK-64), so my main problem is seismic case. Span - 35m, two steel flanged beam with steel deck, with 4 piles 600mm diameter we have 41.4 ton on pile's end. Argillite have design resistance R=1.5MPa (when it dry R=6.8 MPa, but in our case it's resistance decrease in water, so things are so bad).
We don't have good site engineer, cause this work will make local subcontractor. Try to imagine dumb man with great felling of self-importance, without proper education, an you'll understand me. We've worked with them (awful experience), but corruption + nepotism in local administration, an here we are now with the same subcontractor.
We just want to make things easier to construct, with so many point where they can fail as we can. I'm fully confident only in drillers work skills (they are from other firm).
Angle of our rock layer is about 16-20 degrees.
Same reason, we doesn't trust to subcontractor. We can't control quality of concrete on site (precast piles are from good manufacturer).
Than you, for your reply guys. My problem on work now is "How to drive piles to rock and not to break them and not to slip down". If you can refer to any kind of source with information about "driven pile + rock", it will be appreciated very much.
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
Instead of a pile shoe, perhaps a driven precast concrete pile with a composite H-pile, including an H-pile point:
Then the pile installation is "routine" pile driving.
Is the 16-20 degree slope measured from horizontal or vertical? The above suggestion should work for horizontal angle... not for vertical angle.
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RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
They would not get the socket into rock as a drilled pile would but do the loads require a rock socket. Rock socket is definitely good practice/norm but might not be essential.
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
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RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
RE: Precast concrete pile + weathered rock / How to make a pile foundation in proper way?
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