Placing Tower Anchors in Sandy Soil

[K7LXC at aol.com]

In a message dated 96-11-16 13:01:42 EST, you write:

>I have been studying all of the Rohn recommendations for tower bases and
>anchors, but every drawing they provide has a caveat which says,
>essentially, that all bets are off if you don't have "normal" soil.  They do
>provide a definition of "normal":  "'Normal' soil is a cohesive type soil
>with a horizontal bearing capacity of 400 pounds per square foot per lineal
>foot of depth.  Rock, non-cohesive soils, or saturated or submerged soils
>are not to be considered as normal."  Nowhere, though, can I find a clue
>what to do if your soil is not "normal".

Hi, Bruce --

   Well, looks like you got yourself a worst case scenario.  The sandy, coral
submerged "soil"  has little strength.  While my reference calls it a Class 7
soil, I can't find more info on its capacity.  The "probe chart" that I have
has probe values of 100-200 inch-pounds but I don't think that's the load
bearing capacity.  Any soils engineers out there? 
>
>My soil, as you can guess, is not normal.  It's sand.  To be more accurate,
>it's a mixture of sand and ground up coral with a lot of coral rocks 4"-8"
>mixed in with it.  More than that, I'll be putting one anchor only about 90'
>from the water line, and during a major storm I have no doubt that this
>point will become "submerged".  Looking at the Rohn diagrams, it looks like
>a hunk of concrete 3'w x 4'l x 1'd, buried 3' in the ground, is all that
>they recommend for anchoring my 80' of Rohn 45 in "normal" soil.  Clearly I
>will need a lot more than that to put up my beachfront tower, but how much?
>Does anybody here have experience, preferably successful experience, in
>anchoring towers in sandy soil?
>
     The practical things that you can do are to put the anchors out as far
as possible (the less the angle, the lower the stress) and use a massive
amount of concrete.  You'll need enough to hold about 10,700 pounds (the
breaking strength of the 1/4 inch and 3/16 inch guy wires - 6700 + 4000 =
10,700 pounds).  If the block is big enough, you could just set it on the
ground surface.  If you're going to have water coming at it, have it point
towards the water so that the surf will break around it.  

    Regardless of what you do, you'll probably wind up with anchor creep.
 You need to get an engineer involved and have him or her design you the
appropriate anchors.

    This question is more appropriately posted on TowerTalk, the tower and HF
antenna reflector.  This isn't exactly a contesting question.  Send a message
to towertalk-request at akorn.net with subscribe in the message and you'll be
all set.

    How'd you do in SS?

73,  Steve   K7LXC

   TOWER TECH -- professional tower supplies and services for amateurs

>From tomf at neca.com (Tom Francis)  Sun Nov 17 03:32:24 1996
From: tomf at neca.com (Tom Francis) (Tom Francis)
Date: Sat, 16 Nov 1996 22:32:24 -0500 (EST)
Subject: Drinking Dr. Pepper....
Message-ID: <199611170332.WAA29523 at orion.neca.com>

My own personal opinion of Dr. Pepper is
the same opinion I have of Moxie....

YYEEECCCHHH!!!

Now grape Nehi, that's nectar of the gods!!

73

Tom, NM1Q (tomf at neca.com)
Nehi and a moon pie - can't beat it!!


>From k3lr at telerama.lm.com (k3lr)  Sun Nov 17 03:55:19 1996
From: k3lr at telerama.lm.com (k3lr) (k3lr)
Date: Sat, 16 Nov 1996 22:55:19 -0500
Subject: NEW NA10.12 and MASTER.DTA
Message-ID: <199611170355.WAA11924 at defender.lm.com>

The lastest NA version is on the LTA BBS (412-528-8877).
It is Version 10.12.

The latest MASTER.DTA files from AD1C are also on the LTA BBS.
Thanks to N3RA, MASTER.ZIP, MASUSVE.ZIP and MASTERDX.ZIP have
been taken from the AD1C FTP site and uploaded to the LTA BBS for
those who cannot FTP or use UUencode. The MASTER files are located in
AREA 6, RECENT UPLOADS.

73 and CQ CONTEST!
Tim K3LR

LTA at contesting.com