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Re: Footing Overturning in Rock

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Rich,

Rock anchors is one solution but is more expensive and cumbersome in comparison to using the dead weight of concrete. In a power plant project we had done, we did one structure without rock anchors (the footings were coming out to be 18'x18'x4' but still cheaper than reducing the size and use anchors). The other structure had space limitations so we had to use rock anchors in spite of being more expensive).

HTH

Pankaj Gupta
Structures Online
India



----- Original Message ----- From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, July 19, 2006 3:13 AM
Subject: RE: Footing Overturning in Rock


Rich:

I don't see why you could not use some sort of epoxy (or other chemical)
system to "glue" in rebar into the rock that then could be cast into the
footing in some manner.  The only issue that I would think that would need
to be resolved is if there is any testing/evaluation of epoxy anchoring of
rebar into rock (and if so, what type of rock).  But, I have to believe
that there are such systems and that more than likely someone has an
evaluation report or some testing.  The biggest challenge may be drilling
the holes, depending on the type of rock.

Regards,

Scott
Adrian, MI


On Tue, 18 Jul 2006, Rich Lewis wrote:

Joe,



I'm not sure if you are kidding or serious.  How common are epoxy rock
anchors? I haven't seen them used before. I have been to the Williams site http://www.williamsform.com/Ground_Anchors/ground_anchors.html and looked at
their literature.  It seems to me that there are 2 possible ways of doing
it. One option is to predrill and use pigtails in the footing. The other
is to post install by drilling through the footing into the rock.



I would think wedge anchors would be more reliable because you may not get a
clean hole for the epoxy.  Plus, pumping equipment is needed.



Any other thoughts on this would be appreciated.



Rich







  _____

From: Joe Grill [mailto:jgrill(--nospam--at)swiaz.com]
Sent: Tuesday, July 18, 2006 11:09 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Footing Overturning in Rock



Using those pesky little anchors that we have been talking about the last
couple of days.



Joseph R. Grill, P.E. (Structural)

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying



 <http://inet/index.htm>

-----Original Message-----
From: Rich Lewis [mailto:seaint03(--nospam--at)lewisengineering.com]
Sent: Tuesday, July 18, 2006 9:02 AM
To: seaint(--nospam--at)seaint.org
Subject: Footing Overturning in Rock



I'm working on the design of a simple spread footing bearing on rock. The
overturning moment due to wind is large requiring a large footing to meet
the 0.6*D + 1.0*W load combination.  I was wondering about possible
techniques for engaging the rock to help resist overturning and uplift. Is it feasible to anchor into the rock to do this? Are there other methods to
utilize the dead weight of the rock to help resist overturning?



Thanks for your help.



Rich





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