Pile Driving Survey Standard 3

[phamENG]

Out of curiosity - is there a standard format for pile driving surveys that is widely accepted in the industry? I've always required them, but have thus far not specified anything too detailed for the requirement. As a result, I've had everything from a sketch on what was little more than a used napkin to a nicely formatted DWG showing precise placement overlaid on the original drawing PDF with all tolerance violations annotated.

I'm considering writing such a spec to push the received documents toward the latter's end of the spectrum, but don't want to spend the time if such a standard exists out there in the ether.

Any ideas? Thanks.

 

[structSU10]

it is a document so you can check that the piles were within placement tolerance, and adjust the pile caps / grade beams as required to work with the as-built layout of the piles, or determine if you need to add additional piles.

I have the same experience as you, and handled it the same way in the past. I had never run across a standard for this either, and it would be great to have something explicit so you can know how much effort is involved in working through that data when it comes in.

 

[WARose]

I've never seen such a "standard" either. Usually I'll get/ask for a post-installation survey and the surveyor will provide the locations (in a CAD dwg) and i will adjust my cap design where necessary. Or (in one case some years back) get them to add a pile(s).

 

[WARose]

The project specification should have specified the standards, including testing, tolerance and acceptance criteria.

You always include a tolerance in the specs/General Notes......but that doesn't keep stuff from going wrong.

 

[WARose]

That's part of your management plan, you either pay for the professional work (inspection/supervision), or misaligned piles.

Even with a "management plan" (or inspector)....the chances are excellent you are going to have a few piles (somewhat) out of place.

 

[phamENG]

Thanks, everyone. I'll add it to my to-do list. I'll bring it back and post it here for input and, if you'd like, wider use.

retired - I agree. It shouldn't happen, and there are certainly plans in place to minimize it. But as WARose mentioned, they're never perfect. If you hit an obstruction at 20 feet, you're not going to dig down and remove it and a wood pile won't go through it. So, sometimes, you move it over a little. This results in an out-of-tolerance pile and the cap design has to change to accommodate it. Of course, there are lots of other reasons. Occasionally, the pile driver is just lazy. Other times, they just aren't quite as accurate as they strive to be. Around here, the techs doing the inspecting are more worried about capacity and less about location. In any case, the actual location has to be reported back to the structural EOR. I either accept it, or direct a change to the cap and grade beam design prior to fabricating the cages and pouring concrete.

 

[r13]

pham,

Talk to your lab to tighten the rules on inspection/report. The reason you can't simply rely on the survey upon completion is because, it services as a location map/record that only tells you where the pile ends. How good is that you know how far off is the pile on the ground without knowing it has tilted a few degrees beneath. It will fail on load test though, if you do require every pile to be tested.

 

[phamENG]

Thanks, retired. I agree - inclination is also an important tolerance number to consider. Though that doesn't diminish the importance of the absolute location of the pile butt. If it's 9" off the mark, I'm down to 5" clear on the edge of my cap and no longer meet the development requirements for my rebar to satisfy the strut and tie model that makes the cap work. So if it's dead on vertical but way off horizontally, it doesn't work. But if it's dead on horizontally but way off in angle, it could still be a problem. There's usually enough pile left when driving is done to get a measure of the inclination before cutoff, though. My primary concern (with this post) is the survey.

 

[STrctPono]

I'm with you PhamENG, we require it but don't specify how it needs to be delivered. I don't think it's a standard in the industry because I'm pretty sure that on all my past jobs the GC is the one performing the survey.... not the foundation contractor. Chances are because the requirement was not noticed on the plans/specs and the General didn't write it in their contract with their sub so ended up holding the responsibility. On past jobs, I've gotten PDF's of as-built pile locations where the Contractor has marked the horizontal dimension that it is off from the design. Other jobs, I have received a .dwg file that I was able to overlay onto our foundation plan and figure it out myself. Either works but I feel a bit better about having the .dwg file.

 

[STrctPono]

On a side note, you use timber piles phamENG!? What kind of jobs?

 

[Agent666]

Receiving a cad file from the surveyor is the usual method round these parts. Generally we request an independent registered surveyor. We sometimes give them our grid and pile layout so they can dimension all the offsets.

Otherwise you get contractors interpretation of tolerance and napkin sketches and no assurances on accuracy of the information presented in my opinion.

Get or insist on a real surveyor out there with a proper survey.

 

[HTURKAK]

The answer is YES.. In general pile driving contractors (should have ) inhouse developed standard. I am more familiar with Eurocodes. You may look Eurocode 7: Geotechnical design Section 7. Pile foundations Supervision of construction and tests .

The piling contractor should prepare a job specific method statement together with pile installation and test plan addressing ; (for example for driven piles );
-Design Information such as (pile length,required pile load carrying capacity, pile toe level ,penetration resistance , installation sequence..)
-Monitoring of the installation of all piles .The records shall be made at the site and as the piles are installed. A record signed by the supervisor of the work and the pile manufacturer shall be kept for each pile.
- The record for each pile should include (pile no, type and installation equipment, cross section, length ,date and time of installation including interruptions , the values of driving resistance measurements, number of blows for at least the last 0.25 m penetration, obstructions encountered during piling, deviations of positions and directions and as-built elevations...

I have written installation sequence with bold letters.. which is affecting the final position of the driven piles. If the installation sequence is not well prepared, although the initial position precise enough, the final position may deviate substantially..

You did not define the type of pile ( bored, driven, steel, RC ,..) . There are more specific different standards for bored and displacement piles.

 

[phamENG]

HTURKAK - thank you for posting that. I'll take a look at some of Eurocode and the stated standards. This is a general question, but primarily centered on driven piles.

STrctPono - yes, I use timber piles pretty frequently. I'm in Coastal Virginia, and our soils are terrible. Most of the buildings on shallow footings have some sort of settlement going on - though only a handful rise to a level of structural concern. Lots of old (dating to the 1600 and 1700s) uncontrolled fill sites to fill in swamps and stream beds are littered all over the region. Whether it's little 20ft friction piles in the old muck to hold up a modest house in a particularly bad spot, or 30 to 40 footers getting down into some layers of marine sediment for friction and end bearing for larger commercial, multifamily, and industrial, we use lots of them. Fortunately, pine trees grow like weeds (literally) in this area. I'm looking at a podium with 4 story wood over top right now that is going on timber piles. But then there are the really bad areas - in some places along the rivers the muck can go 80+ feet below existing grades. There's a little single story branch library with brick veneer sitting on 100ft precast concrete piles.