H-Piles Driven to Rock

[GeoPaveTraffic]

I'm involved with a project where the owner specified that the foundation would H-Piles driven to rock.

Rock is limestone with between 2 and 5 feet of weathered rock overlying high quality limestone. Top of weathered rock is about 65 feet below grade.

Foundation includes both straight and battered (3 in 12) piles.

Pile driving has just gotten started good with 4 straight and 5 battered piles driven.

The curious part is that the battered piles are diving further than the straight piles, by up to 10 feet after correcting for batter.

I would not thought it possible that the piles would slide or "skip" on top of rock, but that is the only explanation that I've been able to come up with.

Anyone out there have any better idea? Pile driving has stopped for a couple of weeks while the general contractor gets some of the foundation placed. Just trying to determine if we need to make any adjustments before driving resumes.

Thanks in advance for your ideas/suggestions.

Mike

Mike Lambert

http://www.shannonwilson.com

 

[BigH]

I've heard of H-piles sliding on the rock surface - especially if there is a small "angle". I would think that you could put on special driving shoe - there is one, can't remember name offhand, that is supposed to "chip" into the rock to seat it.

 

[BigH]

Mike: See -

http://www.titussteel.com/our-products/pile-points/pile-points/

 

[BigHarvey]

I would agree if the pile would be sitting directly in unweathered rock, but if you have several feet of weathered rock it might not be the only reason. Have you got boulders above the bedrock ? Is the pile driven with a leader all the way ?

 

[fattdad]

Refer to the following link:

http://www.fellenius.net/papers/092 Fish Hook.pdf

f-d

¡papá gordo ain’t no madre flaca!

 

[BigHarvey]

In Sweden you have soft marine clays with unweathered rock beneath which explains what happened in this story. If I understood well, you have several feet of weatherd material as transition material in the case of GeoPaveTraffic, therfore it's a combination of causes ( I gave two other possible causes, the inertia of the pile compared to the hardness of the ground and/or the power of th hammer might be anotherone)

 

[GeoPaveTraffic]

Thanks to all for the responses and sorry for my tardy reply. Don't you just love unplanned out of town trips/fire drills?

BigH - The rock surface is relatively flat, however, with the battered piles being about 14 degrees the points in the link are something I will check into, never seen them before.

BigHarvey - There is no indication of boulders at the site and fixed leads are being used throughout the driving.

Since my original post I have gotten some additional information from the site. It now appears that the fuel setting on the pile hammer may have been higher during driving of the battered piles. I'm not sure that the contractor didn't increase the driving energy and then just beat the piles further into the weathered rock.

Driving should resume soon. I'll post an update once they get restarted.

Thanks again.

Mike Lambert

http://www.shannonwilson.com

 

[BigHarvey]

Don't forget that for battered piles, you lose energy compared to vertical piles ( this is why they increased the fuel consumption I guess ). Ideally, energy is better controled with hydraulic hammers, particularly with IHC hammers where the hydraulics is used not only to lift the ram but also to set an aditional downward pressure.

 

[GeoPaveTraffic]

Thanks for the responses.

We did some figuring on the geometry and it now looks like the variation in pile length is just due to variations in the top of rock. Not sure that we didn't penetrate further into weathered rock on a couple of the piles, but looks like we were just chasing our tails on this one.



Mike Lambert