RICHARD SOLOMON wrote:
> Let me toss this out for consideration. I too have the situation where I need
> a large hole for an LM-470 base.
> I thought about contacting a "Tree Planter" and getting him to use his big
> Auger to bore the hole for the base. I don't think it makes much difference
> if the hole is round or square as long as the same amount of concrete is
> Or am I totally off base here ??
Nope.. you're right on base. here in Southern California, a lot of
structures (light posts, freeway signs, roller coasters, etc.) get
installed on what are essentially vertical reinforced concrete columns.
Drilled out with a BIG auger, rebar cage dropped in, concrete poured, etc.
Your engineer can tell you what diameter and depth works for your loads
and soil conditions. A lot of times, deeper and smaller in diameter
works better than big and flat (it doesn't cost much more to drill a few
feet deeper, once you've got the machine there and set up).
A fairly common scenario here is upgrading traffic signals. They'll
jackhammer out the sidewalk on the corner, leaving a hole inside the
existing curb about 4x4 feet. Drill a 3 foot diameter hole 20 or so
feet deep, then set rebar and fill with concrete. Then, the lamp
standard gets bolted on top. These have huge canteliever loads (imagine
the horizontal crossbar spanning 3 or 4 traffic lanes holding up the
They can do all 4 corners in a morning.
For smaller jobs, they've got machines that can do 2 foot piers on a
small skid-steer type carrier (think crawler drill for blasting) that
you can get through a 5 foot wide gap between house and fence. I don't
know how deep the little machines can go, but 10-15 feet is plausible,
but you might have to put an extension on the shaft.
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