Underpinning

ch0mpie

OK, so either you or you and your engineer are crazy. If thats really what was shown on the plans your engineer is way out of his league. If that building did not settle as you stated earlier you are so lucky. You are relying on stand-up time of the soil to support the building. The correct method would be to excavate even approach pits (as shown beautifully in Nac's photos), excavate even underpinning, pour, excavate odd of approach pits, excavate odd underpinning, pour, excavate all soil, pour footings, sleep at night. For your own sake I would encourage you to remove those pics from this site and from your company's site, and to have a long talk with your engineer about how not to put both of your careers in jeopardy on the next underpinning job.

jmacd

why bother, ok i will call him and tell him he's crazy. Better yet email me and I will give you his name and number and you can tell him he's out of his league and crazy.

tgeb

Now fellas, let's not get in a dither about a project that has already been completed.

jmacd, welcome to the site, I hope you stick around. It's nice to have another "dirt guy" here.

I do have to agree with ch0mpie, they manner in which the underpinning was performed, (as shown in your photos), is not the typical way that we would have approached that job.

If I do any underpin work I usually break it into 3's and do 1 section skip 2, then come back and do 1 section at a time. This way the foundation is always supported by 8' while the 4' section is being worked on. To my knowledge this is pretty much standard procedure.

Your photos indicate that your crew went beyond the markings and had only one section of soil between two areas of excavated underpinning. You are relying on 3 1/2' or so of soil to support 12 to 15 feet of foundation.

If your Engineer signed off on this, fine.....but if there had been an issue I would bet the disclaimers in his contract would have left you holding HIS bag of crap.

ch0mpie has shown more than a few examples of his work doing underpinning, look at some of his old posts. He knows how to do this type of work correctly and safely. I would say that as far as this site is concerned he is the expert on underpinning.

Though it may come across as aggressive/degrading I know that he is trying to help you to be safe and provide a better product.

Now go to a neutral corner, when the bell rings....come out fighting!

__________________
Tom

www.gebcon.com

Stock

ch0mpie as a muck shifter I have never done an underpin job but would appreciate a sketch of what in your opinion was wrong ,we are all here to learn and your help would clear up the the issue for me .

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neolitic

Tgeb gave a pretty damn good
summary, but do an "Advanced Search"
of ch0mpie's posts for some
in depth. ()
Generally speaking, one wants more
foundation supported than not,
and one keeps in mind that the
support travels up the wall
at approximately a 45º angle.

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jmacd

I took the photo down, I am not looking to defend anybody, could care less. Whats important to me is getting the job done and paid for and doing it the correct way for sure. I don't have a degree on my wall but I have built a few projects so as a rule unless I know the architect is wrong I don't question him. He could know something you guys don't or he could be wrong the good thing is the project is done no problems and we moved onto the next one. I don't mind constructive advise but do mind being called crazy or any other name for that matter. I also don't like so called experts that post on the Internet that are complete strangers to me, they could be an expert or they could be just a no it all that thinks they are an expert. This was a piece of a 187 million dollar project so I don't think the architect is some fly by night firm that is "out of his league". Could he make a mistake, for sure, could my guys dig a little more out than they should of, yes. Will I consider smaller areas of excavation on the next one, if we do a next one, yes. Was it a happy ending, absolutely.

neolitic

Hey, it's the interweb!
You gets what you paid for.

Really though, you can always
check a guy's past posts to
get an idea who you're dealing with.

ch0mpie knows his stuff,
engineers don't take diplomacy
classes though.

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denick

jmacd,

Hi, welcome to the site.

In 40 years of doing this type of work I would say that what ch0mpie and tgeb have described are the "typical"way of doing this work. The guys stated what through their experience is the proper way of doing the work. Which as I understand is a generally accepted practice in the US.

Our concern is always for a brother in the dirt business. Please accept the comments as such.

I will say your excavation was neat, clean and percise. The sign of someone who is thinking about what he's doing. I hope you will continue to contribute.

__________________
Nick

"Every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving" Albert Einstein

dayexco

as usual, a great response nick....2 things we have to remember here...we have a young guy who is busting his balls, assuming he's doing the right thing, proud of it, supposedly has the engineer's blessing.....and shows us his work. i know NOTHING about underpinning, so to me, his efforts looked great. i think we can maybe handle our criticism a touch differently, and trust me...i'm the guiltiest of slapping somebody's chops. guys, this is a GREAT place to learn, AND to teach!!!!

__________________
someday, i'll be as patient as Nick.

neolitic

I'll see about sending you three
to Purdue to teach "Tactful 101."

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ch0mpie

jmacd,
I didn't mean to come across so harsh, and I'm glad that this project was finished successfully. However what you show in that pic is a big no no. Unless I was seeing something incorrectly it appeared that you excavated to an elevation below that of the foundation elevation, directly adjact to the foundation for a stretch of about 20 ft. You than excavated two pits beneath the footing.

My issue with this is not the size of the actual underpinning pits as tgeb mentioned, but that you created an unshored vertical soil face directly below the footing. Think about it, would you send one of your men down a hole without a trench box? Of course not the soil wall might fall on him. So why would you rely on that same soil wall to support a building? No one can accurately perdict when a vertical soil face is going to fall over.

The correct way would be as show in post 27 of this tread by Nac. He excavated to the foundation elevation. Then dug approach pits, (a shored hole for his guys to go down in next to the building), then dug the actual underpinning pits (fully shored as far as I can tell). While they were digging the intermediate pits, you can see the building is still supported by soil at the foundation elevation without cutting an unshored vertical soil face.

I have posted pics showing this as well. I'm happy to answer any other questions about this or post a sketch if this is still unclear as I would hate to see someone on this site have a disaster. I've learned alot from guys on this site and am just trying to return the favor. I'm not bs'ing you guys I specialize in this type of work. Also I'll post some pics later in the week of another type of underpinning were using on a job I'm currently working on.

rino1494

Learning is the key to success

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jnimens

You could install helical piles and underpinning brackets to support the load.
If you to with old school excavation in sections and concrete, then don't forget to dry pack the top 3 inches. Joe Nimens.