"Micropile" minimum diameter

[WAstruc10]

Small diameter steel pipe piles (2 to 6 inch nominal) are fairly common in our region. I have always heard these referred to as "micropiles". However, just noticed 2012 IBC section 1810.3.5.3.2 limits minimum pipe diamter to 8", followed by an exception "There is no minimum diameter for steel pipes or tubes used in micropiles." But the definition of "micropile" in chapter 2 refers to post-tensioned grouted anchors, not driven steel pipe piles, so by that logic I guess the "size exception" is just referring to the pipe casing of a grouted anchor. Is anyone aware of the reasoning behind the 8" minimum requirement? Or how the smaller diameter driven piles are justified to the code official?

 

[JedClampett]

Just guessing, but in the pile section are there driving, testing and equipment requirements? If you imposed those requirements on a 3 inch pipe, you'd end up with a buckled disaster.
The equipment used to drive micropiles is a little more "delicate" and probably not code specified.

 

[jittles]

I don't know the answer, but I am interested to see if anybody has more insight.

Our local building department here has specific official "policies" for each individual micropile installer. They must have some sort of acceptance criteria to deal with permitting these sort of installations, given what the code says. They are fairly restrictive on the acceptable uses for these policies; for instance, typically limiting them to one- and two-family residential installations.