Concrete micro piles with single vertical bar?
Concrete micro piles with single vertical bar?
(OP)
There are both expansive and collapsible soils in my area. All of the drilled concrete piers we have designed have been 10" or more recently 12" diameter with multiple vertical bars. The piers also have lateral ties spaced close together through the active zone and spacing out farther in the non active zone (usually below 6 to 10 ft.) There is one subdivision where there have been lots of problems with homes on collapsible soils, the foundations of several homes have been underpinned with concrete "micro piles". These micro piles are 6-8" in diameter and have a single #6 or #7 bar in the middle of the micro pile. The size is a little worrisome to me, as I thought I read somewhere that the code specifies that drilled concrete piers must be 12" in diameter (though I can't seem to find it now). I can't find anything in the code that allows only a single bar (although it does meet the minimum vertical reinforcing ratio), but more importantly can't find anything that would get you out of the horizontal ties. The ties in our drilled piers and others I have seen are spaced 6-8" o.c. Anyone know what parts of the code they are using if any? Maybe they are just designing the piers based on calculations and not taking into account any code requirements. Either way I would like to hear if others think this sounds as fishy as I do.





RE: Concrete micro piles with single vertical bar?
RE: Concrete micro piles with single vertical bar?
At 6" diameter you would have to use a #3 bar for the ties to get to get a somewhat decent cover.
RE: Concrete micro piles with single vertical bar?
@bridgebuster
there are no ties in these micropiles, a single vertical bar is the only reinforcing steel.
RE: Concrete micro piles with single vertical bar?
You can download the Guidelines here:
htt
PS - micropiles have been in use in the US for some 30 years and are certainly not 'fishy' as long as they are designed and installed by competent and experienced engineers/contractors.
RE: Concrete micro piles with single vertical bar?
Thanks for that link. It has some good information.