When this thread started, I meant to add my observations -- but I got too
busy working on my tower project!
Anyway, here in West Central New Hampshire, we have a mixture of soil,
rocks, and even a little sand (I live 700' above the Connecticut River,
which must have covered our land some thousands of years ago.) The soil
tends to get quite hard about three feet down, then softens up and gets
sandier about four feet down. The rocks can range anywhere from pebble size
to automobile size, though typically the large rocks are about the size of
basketballs. On hills, you can have ledge. Sometimes it's solid granite,
other times it's flakier stuff. Some photos of busted ledge from my anchor
holes are shown on my website, www.wc1m.com, under "Big Tower Project".
A couple of weeks ago, I pounded in 12 ground rods for the new tower. I had
a tractor-mounted Ditch Witch cut three 8" deep trenches, which allowed room
for the Cadweld molds. It also excavated many large rocks near the surface.
I pounded in each ground rod by hand, first with a hand sledge and then with
a regular sledge hammer. I had to stand on a stepladder to get each rod
started. I used a metal ground rod sleeve I got with my Cadweld stuff when I
installed my first tower 9 years ago. It protects the top of the ground rod
so it won't mushroom, and presents a target about 1 1/2" in diameter.
Some rods went in easily, and others were a bear. Time to pound in ranged
from 5-20 minutes. The latter probably happened when I hit a rock dead on.
My sense is the ground rod either splits the rock or pushes it out of the
way. In either case, the rod must be wedged against the rock and goes in
slowly from that point on.
In spite of the rocks, and in spite of using only hand power, I managed to
pound in 11 of the ground rods all the way. One rod stopped at the 7' 6"
mark and would go no further. I just cut off the extra 6". I had the same
experience pounding in 14 ground rods for my first tower. They all went in,
but some were more difficult than others. The odds were definitely against
pounding in 26 ground rods without at least one of them getting hopelessly
blocked early on, but I guess I won the lottery.
Water might loosen the soil a bit, but won't do anything about big rocks.
73, Dick WC1M
> -----Original Message-----
> From: Bill Turner [mailto:dezrat@copper.net]
> Sent: Sunday, October 29, 2006 1:12 PM
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Sinking ground rods
>
> ORIGINAL MESSAGE:
>
> On Wed, 25 Oct 2006 09:55:55 -0400, Bill Coleman <aa4lr@arrl.net>
> wrote:
>
> >The best way is to pound them in.
>
> ------------ REPLY FOLLOWS ------------
>
> Agreed, but not with a hammer. Buy or rent an electric hammer
> drill and you will find it becomes incredibly easy. Here in
> the desert there is a layer of caliche, a layer of soil
> nearly as hard as rock, about two feet below the surface and
> a hammer drill will punch through it with almost no effort on
> your part. Manually driving a ground rod through caliche is
> next to impossible no how much water you put down the hole.
> Don't ask how I know. :-)
>
> Bill, W6WRT
>
>
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