Piling inside an existing building.. 2

[GalileoG]

We're currently designing a one bay steel bracing system to be erected inside an existing building and that means we will have to pile inside building. I have several questions that I would like to pose:

1. We would like to have our two piles spaced as far apart as possible in order to reduce the vertical reactions on the pile and the axial forces on our members. However, there are existing 17" diameter piles in the area. We have assumed these piles are friction piles because of their small diameter. We also do not know their length. My question is: how close can I bring the new piles to the existing piles without comprising its capacity? We estimate that our new piles will be about 3' in diameter. I am sure the answer is one that is extremely complicated and one that requires detailed calculations, but is there a rule of thumb out there? Ideas and thoughts?

2. There was a geotechnical report performed on a parking lot that is about 50-60 meters away from the point of interest. Are the results from this geotech report still applicable? I guess what I am trying to ask is: at what distance from an area that was previously tested would its report not be applicable anymore.

3. Piling inside an existing building poses challenges. I am curious as to what logistic problems I can expect to experience? What kind of piles should I be looking at for ease of erection inside an existing building?

I am sure these are trivial questions to you, but I have little to no experience in subsurface structures! I would really appreciate your thoughts and input.

Clansman

"If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[Ron]

I'm curious as to how you'll get a 3' dia. pile installed inside a building. I assume you have restricted overhead clearance, so a pile driving rig is probably out of the question. That leaves a small pier drilling rig or jacking a steel, concrete, or wood pile into place.

Logistically, putting piles inside a building is a pain.

As for your geotech report in the parking lot, I would not rely on that, but then part of that depends on the consistency of the soil profile in that specific area. Apparently you have not contacted the author of that report,which I think you should do if you can.

To answer your first question, you'll need to know more about the existing piles and soil profile than is currently available. As for spacing of piles, they are commonly grouped together to achieve higher capacity, but that's assuming similar pile types. If you change the pile diameter and depth you can affect the existing piles anywhere within about 3 diameters of the pile...same goes for driving. To get that precisely, again you need to know more about your soil and pile conditions.

A 17-inch diameter pile does not necessarily mean it is friction only. Obviously, if you can get the construction info on these piles, it would be helpful or if you could get old or new geotechnical info adjacent to piles, that would be helpful also. You should be able to do testing to determine the pile lengths and given the geotech info you could estimate the capacity.

Do you know for a fact that the existing piles don't have additional capacity to support your bracing? You might explore that possibility.

 

[kslee1000]

Again, couldn't agree less with what Ron has pointed out.
One suggestion, have you considered micro/mini-piles, which will eliminate head room problem, and suitable for in-door applications.

 

[hokie66]

kslee,

What is it about Ron's post that you "couldn't agree less with"? I found it quite appropriate.

 

[kslee1000]

hokie:

Bad language? "I fully agree with Ron", sounds better, agree?

 

[hokie66]

"Less" is "more", then. Pays to read before you post.

 

[kslee1000]

Thanks, professor Hokie, no desire to argue about grammer or language style here. Have a nice evening and weekend.

 

[GalileoG]

It's grammar, not grammer, watch your spelling too!



Thanks for the response Ron, that was very helpful.

Clansman

"If a builder has built a house for a man and has not made his work sound, and the house which he has built has fallen down and so caused the death of the householder, that builder shall be put to death." Code of Hammurabi, c.2040 B.C.

 

[kslee1000]

yes, TA clanman.

 

[JAE]

kslee1000,
I think you've had a bad thread here. Suggest a nice nightcap or two and then try again tomorrow. Your posts are all very good generally. Have to chuckle at this one.

Take care.

 

[kslee1000]

JAE:

Thanks. Just wake up from a good night sleep
No hard feeling about the language issues. Learning from criticism, not attack, is not a bad thing. Though I would prefer/appreciate more (not less) critique on technical opinions I have offered.

 

[Ron]

kslee1000...everyone in this thread is a "regular" on Eng-Tips, so the chiding is good natured....it's just hard to get that to show in a sterile, written posting. We've all had this at one time or another, and I hope we all grow from such discourse. I agree with JAE that your postings add value to the discussions.

Yes, we're chuckling with you, not at you! And thanks to all for your kind words on my posting....now if only I could get my wife to agree with me on something!!

Clansman...have you been able to find anything on the capacity of the existing piles? Would be really nice if they had load tested one or two of them at the original construction.

 

[Drumchaser]

........Clansman

I have used a low clearance drilling unit for installing drilled shafts in a tight situation, although the dia. was only 24" it is almost certain the machinery exists to increase size if you are inclined to pay the piper. Or you could go deeper, depending on your situation.

 

[kslee1000]

Ron:

Thanks. My praises/high grades for most of your postings were based on the contents you have brought to the forums, and meant to express some gratitude after reading and learning (stealing some ideas) from those excellent, well-thought, works.

Difficult to imagine someone could disgree with a well-balanced person (sensed from your writing) like you though

 

[Ron]

kslee1000...thanks. I learn a lot from these forums....and my wife might disagree with you on the "well balanced" comment!

 

[kslee1000]

Ron:

 

[oneintheeye]

micro piles have gone into shop enviroments (super markets etc) in night and shop has been open next day. Might be worth looking at. They can get very high capacities as well

 

[InDepth]

Here are a few answers

The influence zone of the existing piles depends on the soils. It also depends on how the soils are layered and how the pile friction is distributed between each layer. Typically geotech recommendations indicate 2 to 3 pile diameter center to center spacing (based on largest pile).

I agree that micro-piles are the way to go (or helical anchors) if you need to use them in compression or tension. Th contractor can also splice them is sections (a rebar cage is difficult) If you need shear capacity you will need to use a key to activate passive pressure. It sounds like you are in a sesimic zone, so don't forget to have a geotech provide an ultimate capacity for the micropiles (or specify in your drawings a performance specification - design build)

From a contractor's perspective, a low-drill will probably need to be used. The smaller the pile the better, but they do have Itlian made low drill rigs that can drill 4'-0" diameter piles. Of course if you have caving soils and can't provide a casing a micropile is probably the way to go. Call Dennis Poland from Anderson Drilling (619.443.3891) and he may be able to look at your problem if you provide him a sketch or section cut.

Geotech Report - I would suggest that borings be performed where you plan on installing the foundations....so you can at least have design values to work with. With micro-piles you may be able to install them, load test them, and if they don't work, extend them further until you reach the desired design load.


Also!!! Don't forget the steel erection section. Will you need to cut holes in the roof to drop the columns? When you erect th column, what are you weld details? Will you have access to the other side to weld? etc..... etc...

 

[someengineer]

I am currently working on a project in Northern British Columbia where we are using micropiles inside a building in order to replace an exisiting (degredated) foundation. We are taking a low clearance drill rig right into the building and drilling directly through the floor.

I too would like to endorse the use of micropiles.

http://www.dywidag-systems.com

are very helpful if you have any questions in regards to them.

We are using small diameter uncased piles (35mm piles, with 150mm microsil grout). DSI can produce piles with large yield strengths and multiple piles can be cased togther to get even larger resistances.

I would recommend obtaining a comprehensive soils report of your site if you use micropiles, since they rely primarily on skin friction in order to develop compression or tension resistance.


Hopefully this can give you some insight into some other options.

 

[csd72]

We just put some 350mm(17") in situ concrete piles only 600mm (2'-0") from an existing internal wall inside and existing house using a mini drilling rig.

For a larger pile they would definately had to use a larger rig and therefore would have had problems doing it.