[TowerTalk] Guy Anchor Failure

Tower2sell@aol.com Tower2sell@aol.com
Tue, 02 Jan 2001 11:42:33 EST

In a message dated Tue, 2 Jan 2001 10:48:08 AM Eastern Standard Time, Pete 
Smith <n4zr@contesting.com> writes:

<< At 10:02 AM 1/2/01 EST, Tower2sell@aol.com wrote:
>Some people have forgot their science today. If you have a concrete anchor 
>underwater, it has less uplift capacity. To figure the submerged capacity
>subtract 62.4 lb/cubic foot from the volume/density of the concrete and soil 
>mass. This is about half the capacity of a  normal dry installation. This 
>means an anchor designed for dry conditions may pull out when submerged.

Sure, but a concrete anchor 1/2 cubic yard in volume (13.5 cubic feet)
still weighs over 1000 lb when completely submerged.  I'd a helluva lot
rather have that much uplift capacity than the submerged weight of a screw

73, Pete N4ZR
Contesting is!


Screw anchors can work in a similar fashion, the controling issue is either 
the bearing stress on the plates or the weight on the inverted soil cone, 
whichever is less. In other words the anchor may cause the soil to flow 
around the plates or the anchor may lift the entire soil mass. The anchor 
capacity rating is the structural capacity of the steel rod. the actual 
capacity is soil dependent. There is normally an safety factor of two for the 
guys and anchors. This means that if the gound becoes submerged (assuming 
original design was for dry condition) the weight of the resisting soil is 
about half and the foundation (anchor) becomes the weakest link in the 

If the rods are rusted then all bets are off. 

For these failures, I would love to know if copper ground rods were used and 
if the ground was wet. Copper ground rods may cause the anchor rods to 
corrode and wet conditions may accerate corrosion.


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