Extent of Micropile or Helical Pier repair

[RFreund]

When the use of micropiles (or pin piles, helical piers, etc) are used to repair a portion of an existing foundation, do you typically only use piles at the portion of the foundation that needs repair or do you extend the piles to a larger portion of the structure to avoid differential settlement.

Say for example the movement of the structure is isolated to one wall or a portion of a wall. There is cracking of the foundation walls and observed vertical movement. Say the movement is due to either soil desiccation or settlement of poor soils. If you only install piers at the location of damage is there concern of differential settlement or does this go by a case by case basis? I suppose a few borings are in order to determine this?

I thought this came up before but I can't seem to find anything. I have seen this done both ways - where piers are extended to both bearing walls of the structure even though only one wall has distress and where the piers are only located at the area of damage. Curious to hear others opinions.

EIT

http://www.HowToEngineer.com

 

[SlideRuleEra]

RFreund - In my area (coastal South Carolina), there is constant demand for foundation repair because of wide-spread poor soils. Both push piers and helical piles are used by various companies. Their repairs are normally made only were the settlement has occurred, not adjacent areas. Minimizing the number of piers / piles is likely a compromise to keep prices competitive, but the repairs are usually successful.

One company that has decent engineering information available is Ram Jack, for their helical piles. Their website offers their Engineering Manual (registration required, but free). I have a 10 year old version of this manual, its about half self-promotion and half decent info on helical piles. Worth taking a look at:

http://www.ramjack.com/engineer-portal

About finding past threads on Engineering Tips... there is an easy way, use one of Google "Advanced Search" options to narrow all results strictly to ET. Here are the results of an advanced search on "helical pile", try the same for "push pier" or any other specific subject:

https://www.google.com/search?hl=en...lo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=

http://www.eng-tips.com&as_occt=any...ite:www.eng-tips.com&hl=en&as_qdr=all&start=0

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[cfrazao]

I'll have to agree with the above.

We (EagleLIFT) are a General Engineering Contractor and provide the engineering and installation of push our helical piers to our clients. Typically with residential, we will pier or underpin only the areas showing subsidence at the time of inspection. We always provide the option of stabilizing the entire foundation to minimize the chance of differential, however due to budgeting issues it's very rare that the homeowner opt for it. However, in that case, we do have it in writing that they opted for treating only the areas showing subsidence at that time and that other areas of the home may experience movement in the future.

 

[RFreund]

Thanks to both of you for the information.

EIT

http://www.HowToEngineer.com