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

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Digging a 5'x5'x7' hole in sandy soil
From: "Roger (K8RI)" <K8ri-on-TowerTalk@rogerhalstead.com>
Date: Wed, 14 Aug 2013 03:08:02 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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?


I'm not sure where the previous answer went, but it never showed up on this end so one more time.

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 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.

I'm welding and tying/wiring up the rebar cage, but getting a contractor to dig the hole, set and level the cage, coordinate the pour, haul away the dirt and fix the damage to the yard. I also have a large dirt/compost pile that needs to have the top foot removed. IOW I'm taking care of the work
I can still do, but hiring the rest.

I had a volunteer for digging the hole, but then I still would have to set the cage, get the concrete, and then hire the contractor to haul away the dirt, compost pile, and fix the yard.

Were I 20 years younger, I'd be looking for 5 or 6 acres to build a new, larger home on and develop an antenna farm and maybe get myself some toys to dig the holes...and other stuff.
Back then was before retirement and I had a good Job that paid very well.

As to another question, No, sand is not always sand, or at least not with the same characteristics.

Dry sand has very little resiliency. Wit sand, holds its shape and can support quite a bit, EXCEPT where movement is concerned. Remember how wet beach sand can support you, or even a vehicle quite well, but wiggle your toes and your feet can sink in to the point where it takes a healthy pull to get them out. It supports the Jeep, but pop the clutch and it just drops down and goes nowhere. The problem with tower bases is they are continually moving. Although the movement is very small, it's still enough

As I mentioned above and someone else also mentioned a base specifically for sand. Sand lacks the cohesive ability to hold the base, so I would expect the base would need to be large enough to overcome the overturning moment mostly by itself without relying on the surrounding soil for much support.


73

Roger (K8RI)
Thanks - Jeff

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