Auger Cast Pile Installation Clearances

[n8engr]

I am running into some problems with a project involving auger cast piles. This involves a new pipe rack we have designed that will be placed within an existing refinery. There are many places that have either existing foundations nearby or existing piping running about 1'-0" above grade.

The geotech report called for piles to be used so we had no choice in that matter. We decided to go with auger cast piles with the thinking this would be the best option for installation with existing objects nearby.

The contractor has expressed concern with being able to install these piles as he wants a 4'-0" diameter safety cage around the auger during installation (piles are 12" dia.). This cage goes into the ground approximately 1'-0". This obviously will not work due to nearby interferences. My question for you all is...is this typical for ACP installation? Do you know of any alternatives I could offer to work around existing foundations etc.? See attachment for details. Thanks...

 

[ishvaaag]

This kind of precaution may have been derived either from safety at works or asked warrant against any damage. If you can't avoid that, investigate if using grade "centering" beams upon feasible groups of piles may work.

 

[DRC1]

I don't think what he has is a safety cage. He is probably using a conventional crane with box leads. There are Beam leads that will work, as well as specialized drill rigs. However, insatlingt augercast in tight working araes can be difficult. there will be grout hoses hanging from the auger, and rebar cages will need to be picked up and swung into place. Some other foundation options may be vibrated H-piles or minipiles.

 

[hokie66]

Redesign of the piles and pile cap would be required, but it should be possible to shift the piles further away from the piping.

 

[BigHarvey]

I suppose the job is in UK where these safety cages are mandatory for small diameter drilling. I don't think it's mandatory for CFA rigs but I work in France . France has been fighting ( successfully ) at european levels to prevent this ridiculous solution to be imposed in other EU countries. This is a typical example of situation where safety cages can't be used, so contractors remove them and in case of an accident it's a serious legal problem for the CEO of the company !. There are other solutions to ensure that workers working aroud the rig can be safe ( see drilling rigs guide on the SOFFONS website in France )

 

[apsix]

If it is in the UK it would be CFA, not ACP.

 

[BigHarvey]

apsix

Good point ! But I have not seen any other place where a safety cage could be mandatory. If it's not, then they just have to remove the safety cage.

 

[InDepth]

Why not remove the cage and put up a fence?

 

[n8engr]

Thanks for all the info. As usual the story was totally wrong by the time it went from the sub-contractor to the contractor to the client's project manager to our project manager and then finally to me.

Come to find out, the ACP contractor was acutally concerned about getting his rig into tight spots to drill the holes. Have any of you ever seen auger cast piles installed with a rig that has an articulating boom on it (for hard to reach spots)? I'm looking for a piece of equipment that can sit on top of an earth dike and drill holes on the slope. If so can you provide any links or other information? Thanks...

 

[rchanke]

If physical site constraints prohibit ACP work with the available equipment, then perhaps a Micropile alternate could be entertained. Micropiles can be installed with much smaller equipment but expect your project cost to increase.

 

[dirtydude]

Try these links for excavator mounted ACP systems:

http://www.iceusa.com/index.cfm/p/p...2F-4656-955F-E9C244B22A0E/modelname/EM-27.htm

http://www.kellytractor.com/eng/products/foundation_drilling/drilling_tools.aspx

 

[DRC1]

ABI also makes excavator mounted augers. See the Hammer & Steel website

http://www.hammersteel.com/abi/auger.html

for more detail.
How does this get to be your problem? Shouldn't the ACP contractor be figuring this out?

 

[lawayosh]

I concur that the ACP contractor should be the one determining means and methods/equipment. This is how estimators are supposed to earn their keep. Coming up with ways to get any type of pile foundation installed in odd or tight places is the fun part of estimating that type of work. In some cases we would be trying to sell the idea that deep foundations were preferable and even possible.

 

[rchanke]

From a contractor’s perspective, the engineers at times specify a design that may work on paper but just can’t be done in the field without incurring significant difficulty and cost. Design Engineers should do their homework by not being shy in asking contractors what equipment limitations there may be. By doing this they earn their keep and bring value to their client or project owner.

 

[n8engr]

I agree with everything you guys are saying with regards to looking into constructability issues, etc. before finalizing the design.

The reason I'm in this situation is because the guy who did the engineering left our company once the package was issued for construction. I was not involved with this particular project in the design stages and was trying to keep the client happy while also finding a solution to constructability problems.

After talking with the contractor some, it looks like we may have worked through any issues that he had. Thanks again for all the input.