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

[Peter Fels And Phoebe Palmer]

Thanks for the responses Ralph Mike G and Mike S.
The idea of converting  the pulse to a low frequency wave is 
disconcerting. I was hoping to quell that with the 2 big unequal and 
uncoupled concrete masses with squishy stuff in between.
As Mike says, my concern wasn't so much the tilting of the hammer ( 
though centering the anvil is a good idea) as sliding, shop and all down 
to the ocean. Because my last place fell into the Pacific, though it 
happened slowly, it tends to be present in my mind, cause it's a whole 
lot farther to fall here.
"Prime NH farm land" LOL....bet there aint  many places in NH quite this 
steep that aren't rock.
A steep lump of clay..was a gross oversimplification. The Dr of Geology, 
a University professor, shrugged and grinned at me and said " it ought 
to out-last you".
Geologically, this place rests on the scrapings that pile up on the 
Pacific plate as it subducts under the contenental plate..I think. 
Consequentally it's  crushed and mixed and tumbled with layers and lumps 
all topsey turvey.   There are 2 kinds of sandstone, chert, yellow and 
grey clay, pillow lava and serpentine all within  a hundred feet of the 
shop. Imposed on this are a series of prehistoric beaches from when  the 
sea was higher or these mountains were lower.
While I have some hints as to what's under me from digging pads and 
foundations and the like...how much of what is where isn't apparent. I 
doubt that there's a way to calc it  out within  my sorry budget.
There's no way for me to know how much water is  perking through  the 
layers of shattered rock to what layers of clay and where they are. 
That's why I have 280 feet of culvert staked to the hillside conducting 
our drainage to the creek.
Here's the URL to  a helicopter view of the place from off shore...I'm 
on the right....I lucked out, it doesn't show my junk.
http://www2.californiacoastline.org/cgi-bin/image.cgi?image=1689&mode=sequential&flags=0
 From your responses, I take it that my multi-layer damping foundation  
idea ,isn't gonna cut it...sigh.
Perhaps I'll have to suspend it from hot air baloons held aloft by the 
forge exhaust heat. Gonna be hell to use on a windy day.
Appreciate the help...........Pete F


Mike Spencer wrote:

>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.
>
>  
>