if the hole is verry big and you have fear of it caving in, use bentonite,
mix it with water and itl set up like thick hair gel, itl hold the sides
open till you pour, if you use this method youll hafta rent a pump truck to
pump concrete into the bottom of the hole (pour from the bottom up) and itl
force the bentonite/water mixture out of the hole
----- Original Message -----
From: "Lee Noonan" <firstname.lastname@example.org>
Sent: Sunday, July 07, 2002 9:31 AM
Subject: [Towertalk] Hit water digging hole - advice?
----- Original Message -----
From: Lee Noonan
Sent: Monday, July 08, 2002 12:04 AM
Subject: Re: [Towertalk] Hit water digging hole - advice?
Mine caved in a few times ..... We had a very wet winter... and in the end
it was SO BIG, that I obtained approval (by the local council engineer) to
make up 3 round tapered metal cylinders from galvanised steel sheeting.
(from an old above ground swimming pool )--- they were roughly 2 feet each
in diameter at the top and maybe 2ft 8" at the bottom....also they didn't
sit on the bottom of the hole (which kept getting larger ) and the sides of
the hole had to be tapered out at the bottom... so it couldn't be pulled out
of the ground... then there was one piece of heavy reinforcing steel mesh
across the top ,plus 3 lengths of reinforcing rods (one in each cylinder)
they were all welded to the tower attachment points... then another 8 inches
(approx) of concrete on the top....
So, there was approx 6-8" of concrete at the bottom and up to the top of
the three metal cylinders (In between the metal cylinders was filled with
the clay I had dug out of the hole..) & the three heavy mounting points were
welded to a piece of reinforcing square mesh steel..... plus one long piece
of reinforcing rod (about an 3/4 or 1" diameter) in each cylinder , also
welded to the mounting points.... I believe I also welded some scrap steel
to the 3 steel rods to make sure they didn't ever pull out..... I can't
remember if I welded anything at the bottom of the hole!!! apart from on the
rods.... I don't think so, as it would have been VERY Difficult to get down
there..... I hope this may be of some help..... The original hole size was
to be about 5ft round or square ... not sure.. and 6ft deep.......The
steel sheeting was just screwed together ..... Its very difficult to
remember exactly .... ..
Maybe all you need is a sheet of flat galvanised steel made to fit Your
hole..... or anything else handy...
I would taper it out at the bottom slightly... ... otherwise You are just
depending on the weight of a square block of concrete to hold Your tower
Lee Noonan VK2LEE
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