Pile Foundation on Landfill

[palesezt]

Dear Friends,

I am new to the group, so please bare with me. I am a strcutural engineer by education and have been working in the railway industry for 15 years. I am very active in my community for youth sports. Although not active with the wrestling organization, I know many members from baseball and football. Now for my problem.

The wrestling organization is looking to construct a 140'x50' pre-engineered steel building on 7 frames, i.e. 14 footings. The selected spot (site plan already complete) has been determined to be on an old landfill. Borings indicate fill with debris down to at least 27'. Historical information leads us to believe that virgin soil lies 35'-40' below grade. A contractor has indicated that wood piles 40' will support the building. They obviously need a design certified by a PE. They have asked for my assistance, at no fee of course, as they are not-for-profit. I do not mind as it is for the kids.

I do not have a tremendous amount of experience in this area, but used my training and some research to determine that:

1) 14 - 50'x12" wood piles will hold the design loads (just the steel building and live/snow load). This was done using a very conservative analysis.

2) A design needs to be done for the concrete slab that will only have to support people.

I am planning to design a foundation slab with WWF and a perimieter grade beam (reinforced but still need to design). My first question is what is the connection detail from wood pile to grade beam to steel frame (4 anchor bolts per footing, i.e. half of the frame). Does the grade beam just sit on the wood pile. I will calculate the uplift force versus the weight of the grade beam (and of course pull out from the anchors).

I am asking for any insight to my specific problem, or the problem in general as it is being done pro-bono for children. Obviously safety is paramount. I thank you in advance for any help you have to offer.

JP

 

[ACtrafficengr]

this is out of my area, but a few things occur to me:

Is this a capped sanitary landfill? Are there any hazardous materials present or suspected? Will driving piles allow leachate to leave the landfill? If so, you may be held liable for groundwater contamination.

------------------------------------------
"Come to think of it, there are already a million monkeys typing on a million typewriters, and the Usenet is NOTHING like Shakespeare.

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[palesezt]

Thank you for the quick reply. I have not been that involved up until now. It was apparently a very old trash dump (25 years or more). It is not an "engineered" landfill. So no cap. I will have to ask the planning board more to understand the history.

Thanks again.

JP

 

[dik]

In addition to chemical problems, there is the possibility of methane gas and you may have to vent the building site. Also, consolidation of fill material may pose an additional load on the piles.

Dik

 

[SlideRuleEra]

palesezt - Are you saying the plan is to use 14 piles (total) to support a 150' x 50' building?

http://www.SlideRuleEra.net

 

[PEinc]

"Historical information leads us to believe that virgin soil lies 35'-40' below grade. A contractor has indicated that wood piles 40' will support the building."

I wouldn't design based on historical information, especially over an old landfill. You have no idea what is below the ground surface or how deep (in addition to the other unknowns listed above). Concrete rubble, rock, wood, old cars, refrigerators, asphalt chunks, methane gas, chemical drums? Can piles be driven? Will the slab also need piles to prevent excessive settlements as the landfill debris deteriorates?

You need to investigate the subsurface conditions.

 

[palesezt]

Thank all for the replies. Regarding the building size and footings, it is a preengineered steel frame buidling (140'x150') that requires 18 footings, 7 on each side and 2 additonal at each gable end. The dead, live and snow loads, factored, result in less than a 20kip load on the footing (in this case the piling). Then of course a slab with separate footing would be required for the interior of the building which would have a couple of partition walls and just open space for wrestling mats.

Regarding the sunsurface conditions, I am very concerned about that. Four borings done previously only went to 27' deep where trash was still found. I have been told (and that concerns me) that the virgin soil is believed to 35-40' below the surface.

As is always the issue, this is a NFP organization and they are trying to minimize cost. If they need to do more borings, I will have to have them do it. I was originally thinking that I would monitor a test pile and do some sort of sustained load test before going all out.

Anyone care to give me ahint on the steps they would take ...

Thanks again all.

JP

 

[VoyageofDiscovery]

Hi palesezt,

Not to rain on your parade, but this site stinks especially for your situation, no pun intended. A not-for-profit organization may be biting off more they can chew. Carrying out a building construction on such a site, with a shoe string budget is like someone selling you land in a bog. It will cost a lot of money to do any type of engineering.

Construction on this site may also contaminate any groundwater, another pr fiasco. Advise to do this on proper fees and engage professionals, not a "Contractor". Doing otherwise will be inviting trouble.

Just my 2 cents.

Regards

VOD

 

[VoyageofDiscovery]

Another very real issue,

What will be your buckling length in this trash?

Just a question.

VOD

 

[ctmtwilliams]

Based on my experience with landfill projects I have the following concerns:

Unknown total depth of the fill material.

Although you indicate a non-engineered cap, but not knowing what the material is that overlays the site, it is possible that material at the surface is indeed acting as a cap. I would do test excavations/borings rule out if this is occurring or not.

Being able to actually get the piles to depth. You have no idea what drilling/driving conditions will be from one pile to the next. As previously stated cars, concrete block, ANYTHING may exist in the fill.

Maintaining the integrity of possible lining material at the base. Again, although there may not be an “engineered” liner, it is possible that the material underlying the fill could acting as a impermeable zone. This is a similar issue as the cap with much greater liability issues.

Reaction of leachate with wood piles?

Methane gas mitigation is a huge issue; it can be dealt with, but can be costly. Potential methane infiltration into occupied spaces is a major safety issue. Here in Southern California in areas where methane gas is an issue, many builders in methane areas opt for raised floors with venting systems rather than slab on grade.

For a slab on grade, you will need a membrane under the slab to prevent methane from eluting into occupied space. Also a diversion system under the membrane (similar to a drainage system) is employed to direct the methane to the perimeter of the building. Additionally, methane detection systems are required in any areas where methane accumulation could occur.

Finally, are the local officials even going to allow construction on a landfill to occur??

 

[GeoPaveTraffic]

I agree with VoyageofDiscovery, this is not the site for this type of organization.

As for the piles, assuming that you can get the piles installed through the landfill (a VERY BIG assumtion)the downdrag load from the settlement of the land fill will be many many times the allowable load on the piles. Also, you must have boring past the proposed bottom of piles to have any idea that the soil can support the proposed loads.

A possible option might be to install a mat foundation for the building. This would need to be done with the full understanding that the building will settle, i.e. all of the utilitiy connections would need to be flexible and the NFP would need to be fully on board. If needed the building could be mud jacked back up to a more acceptable level.

All in all, old landfill sites make a better park than building site. That said, construction is still possible, however, a NFP on a limited budget is not the best owner for such a site.