[TowerTalk] Tower foundation and bedrock

[Grant Saviers]

Since soft rock may not be strong enough in tension for grouted or 
epoxied anchors, perhaps a bit of caution or maybe some consultation 
from a soils engineer.  Anchors are A+ in solid granite and cured 
concrete.  We had some holes drilled with an air powered drill + trailer 
compressor in Adirondacks granite to anchor a cantilevered deck over a 
lake.

Grant KZ1W

On 4/8/2019 13:41 PM, Charles Lind wrote:
> Tower talk has been great for ideas.  The property is in the general area
> of a limestone quarry, and the owner, my brother-in-law-says he has never
> been able to get more than 3 to 4 feet before hitting rock.  The good news
> is he has an excavator, so soon we will make a trial dig to see how deep,
> and how solid the limestone is.  If the rock is solid and at least 3 feet
> down, I like the idea of epoxy and big rebar.  If the rock is in chunks,
> then the dig goes on!!
> 
> On Mon, Apr 8, 2019 at 12:32 PM <k7lxc at aol.com> 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.
>>
>>      What sort of shape is the bedrock in? Is it shattered? How big are the
>> pieces?
>>
>>      If you have to use "extreme" techniques to get the bedrock out, why
>> are you removing it? You want your tower to have a 3000 PSI concrete base
>> and most rocks are equal to or more to that. Why excavate a hole of heavy
>> material and then refill it with different heavy material?
>>
>>      If this was my installation, I'd drill holes into the bedrock, epoxy
>> in a bunch of rebar (you could even use a concrete adhesive to bond the
>> rock and the concrete) and then fill the 3' hole with concrete with the
>> anchor bolts in it. Voila! A yard or two of concrete and you have a 100%
>> reliable, simple and cheaper tower base. I'm just saying.
>>
>> Cheers,
>> Steve     K7LXC
>> TOWER TECH-
>> Professional tower services for amateur and commercial
>> Cell: 206-890-4188
>>
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