Fred McKenzie wrote:
In article , Dave Lemper
wrote:

The soil in central Texas is called Caliche with a lot of clay,
CaCO3 & shale. Attempting to drive in a ground rod
yielded only a mushroom on top & blisters on me.
Local tool rental place has concrete bits, but maximum
length of 18 inches. Possibly longer bits are available in
a larger city.

Dave-

Last year there was a discussion here about sinking a ground rod using
an "SDS Plus" Hammer Drill set to hammer-only. I think it was Ian
White, GM3SEK, who proposed that method.

The other point was that SDS+ bits are available up to 1.0 metres long,
so by using both rotary and hammer action you can drill a pilot hole
through most kinds of rock down to that depth.

There is also an article at
http://www.n4lcd.com/groundrod/ that proposes a slightly different
method of coupling the hammer drill to the ground rod.

The question is whether Caliche can be penetrated by such a method. Has
anyone tried it?

We don't have caliche here, by that name, but from accounts on the web
I'd doubt if it could be penetrated by hammer action alone. However, it
seems more likely that an SDS+ bit could drill through it.

Another consideration is whether or not there is moisture in the soil
below the Caliche. If not, then it might not provide a low-impedance
ground even if you could penetrate it!

That is certainly the problem at this QTH, where an earth rod drilled
and hammered into the very rocky subsoil produced a resistance of
500ohms! Long horizontal electrodes are the only kind that work at this
QTH.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

While I don't have any 'caliche' on my property, I am blessed with a
lot of randomly placed rock. Driving any ground rod to about 6 feet
is a guessing game more than anything else. I've found that ground
radials are more practical. Not easy, just practical. They seem to
work as well as any ground rod I've ever used (better in some
instances).
The local power company is supposed to put down ground rods for
safety. Having seen some of their methods, I'd tend to go with the
radials (ground wire attached to water pipes... PVC water pipes, great
idea huh? And, NO, I'm not kidding.)
- 'Doc