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Re: [TowerTalk] FW: Digging a 5'x5'x7' hole in sandy soil

To: towertalk@contesting.com
Subject: Re: [TowerTalk] FW: Digging a 5'x5'x7' hole in sandy soil
From: Michael Tope <W4EF@dellroy.com>
Date: Thu, 15 Aug 2013 09:07:56 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I have some property in the high desert north of Los Angeles that is nothing but sand. When I was getting prepared to take delivery of a 40ft storage container, a concrete contractor who did some work for me recommended that I have the sand packed before bringing an 18 wheeler on to the property. The guy who did that work for me was a soil engineer who mentioned having just done a hole for a customer's crank-up tower. Surface packing to accept a heavy vehicle is pretty straightforward. You wet down the area to be packed for a day with sprinklers and then come in with a heavy tractor and roll back and forth over the wet sand repeatedly to pack it. For building or tower foundations, Sal described the procedure, but I forget the specific details.

73, Mike W4EF..........

On 8/14/2013 7:16 PM, Matt wrote:
Just want to reiterate on advice from N6SJ, AB7E, KK9A, & VE4XT...  get with
a qualified structural engineer if there is any doubt about the compressive
strength of the soil you are placing the foundation in.   Sand that
collapses upon excavation is reason enough to have doubt!   Insufficient
footing support for the foundation can result in the foundation leaning,
failing, or overturning at less than design load.

Matt
KM5VI


-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Roger
(K8RI)
Sent: Wednesday, August 14, 2013 9:08 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Digging a 5'x5'x7' hole in sandy soil

On 8/13/2013 6:57 PM, jeffhook@comcast.net wrote:

To all:



I have a used US towers HDX 555 I'm installing .

US tower sent me new anchor bolts and a print of foundation and it says
undisturbed soil and forms can't be left in hole.
I live in a sandy area and wonder how others have dug a 5x5x7 hole,
installed reb ar cage, and filled with concrete, without it caving in?
Are these showing up. I never see them.


There are times when it is not possible to pour into undisturbed soil. I
would ask them(US Towers)  specifically what they recommend to use in sand.
They may recommend a larger base. but you might have to resort to
commercial, metal forms.  After the pour cures "enough" the forms are
"pulled" which of course takes some power and maybe the services of a
contractor.

Because of the unstable soil, I'd want a larger base and as someone else
suggested, a base specifically for loose sand would resort to the metal
forms even if I had to hire a contractor.

Where I'm putting up the LM470, the soil should be firm enough to pour
against the side of the hole (undisturbed soil) but the concrete will need
to be poured right away.  Even a light rain could cause it to collapse. I
only have to go 15 to 20 feet West or north and it becomes more of a peat.
When I dug the holes for the 45G guy anchors, I went back the next morning
and the NW hole had become about 12 feet across and 1 foot deep.


73

Roger (K8RI)
Thanks - Jeff

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