[TowerTalk] Tower base over ROCK (shale) experience??

[john at kk9a.com]

It is probably less money just to jackhammer the hole(s) to the factory
specifications.  My house in Aruba had very hard rock/coral ground and the
holes were put in by hand by a local using this method. There are also
attachments for a Bobcat that will break up shale.  What has the original
poster tried so far?

John KK9A



To:	towertalk at contesting.com
Subject:	Re: [TowerTalk] Tower base over ROCK (shale) experience??
From:	"Joe Subich, W4TV" <lists at subich.com>
Date:	Fri, 13 Oct 2017 19:35:58 -0400
List-post:	<mailto:towertalk at contesting.com>
On 10/13/2017 3:53 PM, bear wrote:

> Hiring a soils engineer and PE is beyond the scope of the budget at
> present.

You really need to bite that bullet.  Shales have a wide range of
strength and you need to know exactly both the compressive and
tensile strength of your particular shale.

this stuff is a step down from bluestone, which is quarried not far
from here... it will break down once broken up, and used as something
like driveway fill, turning from large chunks back into granular
soil in about 10 years, but as found in the ground it is stable.
That is true only so long as no forces are applied.  Both the tower
base (compression) and the guy anchors (tension) will apply forces
that are likely to cause the shale to fracture.

Bottom line, *don't guess*.  Get the soils engineer, pay for the
necessary load testing and have the base anchors designed properly
for the application.

73,

   ... Joe, W4TV