[TowerTalk] (Repost) Engineering advice on above ground foundation

[Joe - WDØM]

Not wanting to continue to re-state the obvious - my initial response 
stated there was a difference between our installations - would be nice 
if you would acknowledge that, rather than continue to pursue the 
"difference".  As a former chief of engineering plans and programs for 
the USAF, I have a basic understanding of failure analysis - but that 
assumes there is a failure.   Then again, I understand the 
"tongue-in-cheek" response you're making.

73,

Joe
WDØM

David Gilbert wrote:
> You have bedrock to help keep your base from settling, and your base is 
> pinned to the bedrock to keep the lateral forces on the tower from 
> tilting the base.   He has a layer of gravel over a water table deal 
> with settling, and he has only the weight of the base to withstand the 
> wind forces on a 90 foot freestanding tower.  The AN Wireless towers (I 
> have one) are spec'd for the foundation to be surrounded by undisturbed 
> soil ... not air.
>
> My point is that the time to figure out whether something will survive 
> is before you do it, not afterward.  Engineering after the fact is 
> called failure analysis.
>
> 73,
> Dave   AB7E
>
>
>
> Joe - WDØM wrote:
>   
>> As I pointed out - similar, but my issue was bedrock, his is water 
>> table.  It's never too late....
>>
>> 73,
>>
>> Joe
>> WDØM
>>
>> David Gilbert wrote:
>>   
>>     
>>> Your foundation is pinned to the bedrock ... his isn't.
>>>
>>> It seems to me that the opportunity for N2WQ to properly engineer his 
>>> installation may have come and gone.
>>>
>>> 73,
>>> Dave   AB7E
>>>
>>>
>>>
>>> Joe - WDØM wrote:
>>>   
>>>     
>>>       
>>>> Hi Rudy,
>>>>
>>>> My situation is similar, although different.  I have an above ground 
>>>> base but without the water table issues.  My problem was bedrock.  The 
>>>> tower has been up for over 5 years without a problem, and has withstood 
>>>> 90 mph gusts that blew out the windows on my home.
>>>>
>>>> http://www.wd0m.com/
>>>>
>>>> Click on Ham Radio, then Tower Project.  I hope this gives you some 
>>>> confidence that it will work!
>>>>
>>>> 73,
>>>>
>>>> Joe
>>>> WDØM
>>>>
>>>>
>>>> Rudy Bakalov wrote:
>>>>   
>>>>     
>>>>       
>>>>         
>>>>> Looks like first post came out very difficult to read so here it is again.
>>>>>
>>>>> I have a rather complex situation that certainly can benefit from the collective wisdom and experience of this reflector.
>>>>>
>>>>> My property has a very high water table and as a result my builder and I decided to build the tower foundation mostly above ground. Specifically, we dug a hole, filled it with compacted gravel that is above the water table, covered the gravel with very thick sheets of plastic, and inserted 2' styrofoam boards around the base. Then we poured the concrete.  As a result, only about 1.5' of the foundation is below ground, 3.5' are above.  The overall dimensions are 10' x 10' x 5'.
>>>>>
>>>>> Now I wonder what are the additional engineering issues we need to address to make sure the foundation will last and the 90' AN Wireless tower will stay up.  Currently, we have identified the following next steps:
>>>>>
>>>>> 1) Waterproof the concrete using silica based solutions, such as Penetron, Xypex, etc. as permanent solution against water getting into the foundation
>>>>>
>>>>> 2) Add extra waterproofing using tar/asphalt-like solutions to make sure we have extra protection should cracks emerge
>>>>>
>>>>> 3) Add styrofoam boards to prevent against freezing (it gets as cold as -25F in Ontario)
>>>>>
>>>>> 4) Backfill around the structure to create a mound that takes the rain and melting snow water away from the concrete. I have also proposed we layer more plastic sheets about a foot below the mound surface to make sure no water gets near the foundation
>>>>>
>>>>> Any further comments and suggestions will be greatly appreciated.
>>>>>
>>>>> Rudy N2WQ
>>>>>
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
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>>>>>
>>>>>   
>>>>>     
>>>>>       
>>>>>         
>>>>>           
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