Hi, I just found this sub-forum so thought I'd
re-post a question with some more specifics and different questions as this seemed pretty relevant.
So I have to confess, this is a "fun project" to work on in my spare time so the part about work, while not totally irrelevant is less of an issue for me - so the excavate then cover is not really interesting to me. As i mentioned in the previous post, while I am willing to spend some money for safety I'd prefer not to spend a ton of money.
One of the main things I am interested is how to properly support the tunnel. I am quite fine, prefer actually to error on the side of overkill but only to a point (that is, 6" of cement rather than 4" but not .25 meter thick kind of erroring), but so far I have been able to find scant little information that gives detail for a handmade tunnel (lots for subways etc but ... yeah, a bit larger scale than I had in mind). I have dug down about 9ft/3meters and am well below the subsoil and clay and now down into a "different" clay, not sure what to call it. From what I have read a circular or semi-circular/arch would be stronger, but not sure if that applies to this soil - and if i did an arch I am not sure how it
should be supported (a box I can visualize, an arch less so). Any useful thoughts would be appreciated, especially if you know of resources that cover step by step aspects of supporting small/hand dug scale tunnels in "soft" ground!
I am actually considering getting a civil engineer or something? to take a look and give a general idea and some pointers on what is needed (eg would 2x4 boxing every foot or so be ok, does have to be flush with the ground its supporting allowing me to later fill the space with something like cement? or would that space pose more of a danger?, etc); speaking of which, how does one actually go about finding an engineer to do this and what would such a consultation cost? Anyone in the US have suggestions on the "finding a civil engineer" part?
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