[TowerTalk] Anchors into solid rock instead of cement

[Steve Jones]

I've put in commercial microwave towers on mountain tops on bedrock.  We had
a soils engineer bore test holes into the rock.  Then gave the soils report
to a structural engineer who designed the concrete epoxy attachment anchors
based on the rock characteristics.  That's the right way to do it, but not
particularly cheap.  But we had a problem at one site where the borings went
into two granite domes which straddled an area of weathered rubble.  Had to
dig that part out and use reinforced concrete pours for that leg anyway!
Slate doesn't sound as solid as granite.

On the other hand, we had some sites where it was cheaper to pour a "mat"
foundation, basically a big flat rectangular of concrete that sits on the
surface.  The mass has to be big enough to resist the overturning moment of
the tower.

73,
Steve
N6SJ


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of dw
Sent: Tuesday, January 12, 2016 9:25 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Anchors into solid rock instead of cement


Hi All,
As I'm preparing for an installation this summer it looks like, due to my
property characteristics, there is a high probability there will not be
sufficient soil dept to put in cement for either a base or for anchors.  A
large percentage of the property is shallow soil on top of
100+ feet of solid slate bed-rock.

Has anyone seen examples of installations where anchors etc were drilled and
fixed into rock?
I'm probably going to want to look for someone local for the drilling,
unless I can rent a drill myself.
N1BBR
--
 Bw_dw at fastmail.net

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