[TowerTalk] Bedrock

[Mickey Baker]

Sometimes engineers earn their money! Great work!

Mickey Baker, N4MB
Palm Beach Gardens, FL
*“The servant-leader is servant first… It begins with the natural feeling
that one wants to serve, to serve first. Then conscious choice brings one
to aspire to lead." Robert K. Greenleaf*


On Mon, Jan 27, 2020 at 4:02 PM Charles Lind <cxl24 at case.edu> wrote:

> A while back I posted a question about digging a tower base when bedrock
> was (probably) just a few feet down.   The tower was a U.S. Tower TX 455,
> and required a 6.5 foot deep hole.  It was likely that much of the 100
> acres we  had available was on the Niagara escarpment, with limestone at a
> depth of about 3-4 feet.  We got out a large excavator, and indeed hit rock
> at 3.5 feet.  Then got out a bigger excavator and tried to smash the rock.
> Not only was it impossible to even dent it, but the surface was as smooth
> as a highway.  Not to be deterred,  we took a rotary impact hammer with a
> two foot bit and drilled 4 holes at 45 degree angles aiming toward the
> center of the pit, and 4 vertical holes, then drove in 7/8 inch
> rebar--potted in with hydraulic cement.  Over that the prescribed rebar
> cage was placed, although that had to be shortened with the help of an
> oxy-acetylene torch.  Three yards of 3500 psi concrete was placed on all of
> that, and allowed to cure for a month.  The tower was installed without
> incident, and has since survived 60 + mph winds.  Thanks to all who offered
> advice.......
>
> Chuck, N8CL
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