Hi Chuck,
An engineered spread footing can be used instead of a deep hole. Some
of the catalogs for big triangular towers show them. Enough mass and
moment resistance for a self supporting tower can be created several
different ways other than the deep hole off the shelf design.
For DIY to the OTS tower base design, limestone should yield to a
excavator hydraulic hammer or go down in the excavated hole with a large
electric breaker (or an air driven jackhammer with trailer air
compressor but they are a real handful). One of the electrics wouldn't
be so bad as the hole needed isn't much deeper than 3'. Most rental
yards have a Bosch, Hilti, Makita (what I have) or Dewalt on a cart. I
used a bull (spear) point in sandstone, hardpan, and shale, good to have
a sharp spare. (plus eye and ear protection).
A small backhoe or mini-excavator (better, esp. for the conduit
trenching) can be rented to remove the dirt and broken rock. With 200
acres maybe a nearby friendly neighbor's backhoe?
If the rock is granite not limestone, shale, or sandstone, that is a
whole different ballgame.
Grant KZ1W
(Case '66/68)
On 4/7/2019 16:34 PM, Charles Lind wrote:
I have the opportunity to put up a TX-455 tower on the property of my
brother-in-law: 200+ acres and no zoning issues. He says, however, that
there is limestone bedrock about only three feet down. Before I start
Digging pilot holes, is there any advice a how to proceed with providing a
solid foundation if this is the case.
Tnx, Chuck, N8CL
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