[TheForge] Hammer on clay soil (Was: make shift anvil)

[Mike Spencer]

PeteF> We live on  top of  a very steep lump of clay with some rocks in it.

Ah!  Prime New Hampshire farm land. [1]

GHS> You might want to get someone who understands wave dynamics vs
GHS> soil compaction, to help design this. Those longer rolling waves
GHS> could get the same effect that earthquakes can produce, turning
GHS> the otherwise solid ground all liquid for an instant.

The key word here is "thixotropic".  Stuff that's thixotropic is stuff
that is fairly solid when it just sits there but turns semi-liquid (or
very liquid) in response to vibrations.  Some clays (or clay soils)
are and some aren't.  Pete's real concern is not that his anvil might
tilt a bit over the years but that his hammer (or shop or whole
homestead) might gradually (or suddenly) take off downhill.

You can do a crude test of your soil thixotropy by digging up some of
the clay, patting it into a shape and setting it on some kind of table
that you can vibrate with various frequencies -- say, with an air
chisel, electric drill with a bit of crooked rod in it or just some
relentless hand tapping with a hammer.  If your clay shape gently
slumps into a miniature landslide, you know you have a problem and
should consult a soil expert with experience in handling this problem.

Better to find a construction engineer who specializes in soil
stabilization problems and is familiar with the local soils and see if
you can get a free/cheap consult or even a test of some soil samples
from your site.  If your soil is confirmed as very thixotropic,
spending real money on professional advice would be well worth it.

I would have said to go with a layer or three of wood -- maybe 3 feet
rather than 8" under the anvil, perhaps partly endgrain up -- but
Mike Graf's experience suggests that might not neccessarily be the
answer.


- Mike

[1] Yak: New Hampshire farm land

About 1840.  A New Hampshire farmer is driving along the road when he
comes to a rabbit who's sitting in a puddle of tears, crying its heart
out.  Farmer pulls his horses to a halt, shifts his chaw and says,
"Say there, Rabbit.  You seem a mite distressed.  What's the trouble?
What could a feller do to he'p you out?"

Rabbit replies, "Well kind sir [sniff], my father just died and left
me a hundred acres of this prime New Hampshire farm land and I have to
get my living off it."

Farmer says, "Not a thing to be done for you." and drives on.

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer@tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^

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