I know they have been built for 100's of years in all types of sub-soil surfaces. I have never found a book or source that gives the ins and outs of safety, constuction, reinforcing, water table, other water issues, etc. I am pretty sure I could figure it out on my own. Would like to have something I can give to others that has already been proven.
Not looking to do the chunnel or big dig or anything large. something along the lines of an underground path from house to shed etc. say 7' x 4' should be plenty.
Around here, if a boulder can't be moved by a large back hoe, it is jackhammered into smaller pieces. If it's too massive for jackhammering, then it's drilled and blasted with dynamite. From my test holes, I've determined that my rocks can be handled by a back hoe, so I'm considering using one to dig a deep trench for the tunnel. Then I'll form it up for pouring concrete. I'm still debating on whether to use an arched ceiling, or a flat, poured concrete ceiling. On top will be about 18 inches of subsoil and whatever topsoil I have left. Then I'll attempt to grow grass.
A neighbor of mine built a seriously large bunker under his new house. The walls and ceiling are two-feet-thick poured concrete. For my tunnel, eight inches should suffice. I do not plan to use any steel rebar because it rusts and actually breaks up concrete over time. My concrete will be a stiff mixture containing rough aggregate.
If you need to burrow though a mountain (or hill), then my plan won't work for you. I've heard of tunnelers using "Gunnite" concrete to line it, but it requires a special machine for spraying it on. Tell me more about your terrain and the other considerations I mentioned at the beginning.
As I find info, will try to post it back here.
Ted A wrote:I'm still debating on whether to use an arched ceiling, or a flat, poured concrete ceiling...I do not plan to use any steel rebar because it rusts and actually breaks up concrete over time. My concrete will be a stiff mixture containing rough aggregate.
I think not using re-bar tilts the scales toward using an arch.
A flat ceiling will be in tension, in some places. Rough aggregate will help resist shear, and compression is almost never a problem for masonry, but in tension, only long reinforcements will help much.
I've seen re-bar break up concrete, but as I understand it, this is mostly a problem when it is placed too close to the surface of the concrete. The interior is too alkaline to allow much corrosion of ferrous alloys.
Basically they old timers piled up a dirt arch (it was a dome for the cellar , but you should be able to copy it for your tunnel..)
OK you build the arch from dirt, then place rocks in the shape of the arch over the dirt. Pour cement to link all the dome rocks together,
After it dries then you dig out the dirt under the arch.. (lots of work by hand back in the old days.)
I don;t know if there was a footing under the rocks, but it would probably be a good idea.
To give you a idea aboiut building a tunnel is hard not knowing the ground that you are dealing with.
If it is soft ground you will have to rock bolt it and gunite the walls after you put chain line fenceing up(lots of work) or you might be able to timber it? Or put a 8 foot culvert pipe in it But that is big money.
Look up old mining books on Google books and you might find something. Here is a good one
I'm leaning towards the compression of the soil, as it could solve many problems at once. Have to work on a good method. I am sure I can come up with a few.
much of it may not matter as much on a small tunnel. be nice if i could wash out a 6 inch hole, fill it with something that has some kick and make it a 6' hole of compressed and bonded subsoil.
Going to read some books that Whitlock linked to.
Do you have to have the top covered with dirt? or how about an east west trench with a filon or glass side facing south? Kinda like a gable roof over the trench that could also be a green house to have winter greens.
But, you're better off using a shovel and timber shuring for a small tunnel.
Explosives can only be used in a very rural situation, when you need a big hole fast.
Where the Field Are Rock
Something else I've read about is "slow dynamite" which is a safer chemical reaction, safer since it goes so slowly. Faster than ice though. I've thought of dropping dry ice into the water holes but not tried that.
So far all of our projects have been cutting out ledge in an open manner, or splitting boulders. We haven't yet tried tunneling. We have a target spot we're studying.
Every time a big project like the new tunnel in Europe is completed we joke about getting their mole.
Well i lie i dont like being underground and my worry is always of being the thin lubricant between rocks if the roof falls in.
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