[TowerTalk] Pad and Pier Foundations

[ersmar@comcast.net]

Kelly:

     
     There is a trick to getting the equivalent of undistrubed earth performance from earth that's been disturbed.  This is done all the time in the professional (tower) construction industry.  (BTW - most of the cellular tower foundations I've seen constructed were built using excavated, rectangular pad-and-pier construction, while many of the electric utility towers I've seen under construction were built with circular, augured foundations.  I've worked in both industries.)

     The step you left out in your description, below, is tamping the backfilled material after emplacing each half-foot of earth.  This is done in professional applications with a pneumatic or gasoline-powered tamper.  These things look like jackhammers, but instead of a drill bit, they have a heavy flat steel plate on the bottom.  The heavy tool bounces up and down on the dirt to compress it.  

     An alternative that's used for large areas of compaction is running a heavy tracked vehicle over the area to be compacted so many times in two directions at right-angles to each other.   For both of these methods, the design engineer specifies how much compaction is required to restore undisturbed earth mechanical properties to the backfill material.

     Nothin's every easy, is it?

73 de
Gene Smar  AD3F

  


> Yes, they probably use a back hoe.  I suspect the answer to my
> original question about how they build the pad-and-pier holes is that
> they dig the hole big enough for the pad, insert a form for the pier,
> pour the pad and pier, wait for them to dry, then backfill.  My
> original question really was: is backfilling OK for these types of
> foundations?  All foundations I had seen in the past required
> "undisturbed soil" around the foundation.  I couldn't see how this
> could be accomplished for this type of foundation.  I guess
> backfilling for this type of foundation is not only OK, but probably
> the only practical way of doing it.
> 
> 
> 
> On 7/11/05, Alan NV8A (ex. AB2OS) <nv8a at att.net> wrote:
> > Back hoe?
> > 
> > 73
> > 
> > Alan NV8A
> > 
> > 
> > 
> > On 07/11/05 03:25 pm Kelly Johnson tossed the following ingredients into
> > the ever-growing pot of cybersoup:
> > 
> > > OK, I can buy that.  So, if they are spec'ing square holes for
> > > commercial users then those commercial users must have a reasonable
> > > way of creating the required holes.  It seems unlikely to me that they
> > > go down to Home Depot and hire a couple guys from the street to dig
> > > the hole by hand :-)  Anyone know what the commercial guys do?
> >
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