K7LXC@aol.com wrote:
>
> In a message dated 9/13/2009 7:07:01 P.M. Pacific Daylight Time,
> towertalk-request@contesting.com writes:
>
>
>> I thought I read on reflector or in a Tower installation book that
>>
> it is not a good thing to backfill the area around the tower base,
> but looks to me from photos as that was done as concrete was poured into a
> contained wood wall form and then area around
> base filled back in with dirt...
>
>
>> Am I missing something here or not interpreting photos right ?
>>
>
> I looked like they used a form around the rebar cage so they would
> have had to backfill it. Typical tower base specs call for pouring against
> "undisturbed earth" so the forms would have been against spec.
>
OTOH that may not be an option with some soil conditions. For my tower
base I was able to do that, but found we had to use forms for the guy
anchors. I hired a backhoe and operator to dig the holes for the guy
anchors. They looked great, but it was a good thing I checked them the
next morning before ordering the concrete. What had roughly been 5 X 5
X 5 holes were now about 10 X 10 X <12". I think I have some photos of
prep-ing the holes and dropping in the forms. Once in, the crushed rock
was dumped in and inside braces were installed to prevent a
re-occurrence of the hole getting wide and shallow again. Of course the
outside has to be braced as well. Wet concrete puts a lot of pressure
on those forms if there is nothing against the outside.
Where forms are used they should be removed as old, wet and decaying
wood is like grease and leaves a pour with very little purchase on the
ground around it.
> Undisturbed earth has the maximum soil strength - disturbed or backfilled
> does not. You can use a form and then backfill it but it's not easy. You
> have to tamp the dirt back to its previous solidity with powered jumping
> jack
> tamper.
Which may not be possible with some wet soil conditions.
> It's outside of the scope of your average ham tower owner to do it
> properly so I'd recommend sticking with undisturbed earth.
>
> Cheers,
>
73
Roger (K8RI)
> Steve K7LXC
> TOWER TECH
> author of UP THE TOWER - The Complete Guide To Tower Constrution
> available from _www.championradio.com_ (http://www.championradio.com)
> Cell: 206-890-4188
>
>
>
>
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