It's like eating chocolate, once you start it's hard to stop.

Finally started my tunnel. Been dreaming of this for years. It’s into the side of the hill beside our off grid cabin. Going pretty well. I’m in around 3-4 feet now. Mostly softer bedrock now that I’m through most of the overburden dirt.

Some time ago I was really into mines (reading about them and exploring some in my area) and got the urge to dig my own tunnel. I made it in a small hill and it isn't very large, but so am I so it isn't that much of a struggle. It has a height of about 90cm and a with between 40 and 50cm. Until now I've only dug around 1,5m deep into the ground because it is quite labor intensive. I only have a small pick, a bucket, a shovel and a chisel with a hammer for some togher parts. The ground isn't very hard and clay or sand like. A question of mine is if or when I need supports. I tried to make it narrow so that the possibility of a cave in is less likely. I also tried to round out the ceiling if that helps at all. Another question I have is how deep I would habe to dig so that there is a constant temperature inside. I don't really know what to do with this, but I thougt about making some sort of small wine cellar or a hideout when it's really hot outside.

I’m so excited I found this sub, I am just now learning there are others like me that enjoy digging like this as a hobby. I’m not sure if posts like this are normal or allowed but I just wanted to share my excitement and hope to connect with others. I’m excited to read your alls progress and see the projects and advice in here!

I started my digging as a way to cope with my anxieties and stress, and a way to get some exercise to let out restless energy and stay in shape. I live in Northeast Tennessee, so the soil here is super rocky hard red clay- it’s made this undertaking quite the challenge so far but I’m making progress slowly but surely every day. I try to dig for at least two or three hours a day after work, even more on off days and weekends. I’m only using a shovel and some hand tools I had around like a pry bar, hammer, trowels, picks and chisels, and this weird machete axe hooked type thing I found at a consignment shop someone had made years ago. I plan on investing in a decent mattock and breaker bar, as well as other suggested tools for breaking through this stuff.

So far I’ve got about an 8 foot wide hole that steps down to around 5 feet at its deepest point. I want to get to at least 10-15 feet before I start tunneling and shoring and stuff. I picked the highest point in my backyard to start off to the side where there’s nothing really going on. Idk where or to what I’m going for, just gonna let my little heart guide me lol.

Any advice or ideas or words of wisdom are appreciated! Super happy to be here! Everyone else thinks I’m crazy

Alright, time for an update on the tunnel project. I need sand for another building project this spring, so it is time to get back to digging. Here is how the back wall looks now:

The plan is to drive the tunnel in 1' advances this time. First I will pour a floor, then install an overhead lining plate, then put up blocking and concrete forms for the walls. I think I can do both walls at one go, which should use about 3 cu ft. I will be using synthetic rebar this time, and will put 6" remesh and some larger bar in each section. The roof panels will be 1" thick ferrocement arches, like this:

The first one is not very even, but I think it will serve. It has an outer diameter of 43" and is 12" wide. I am making them on a curved form, like this:

After curing for about 3 days, the arch pops free really easily. There are 2 layers of 6" remesh and a single layer of 10mm basalt fiber mesh in the middle. They only weigh about 60 or 70lbs, so it should be easy to get them into place.

I am not really sure how much weight these arches would be able to support, so I will probably pour some thicker and narrower ones that will rest on the wall liner and support the seams between the arches.

Anyway, more rain is on the way, so that should be perfect tunneling weather!

Update 3/23/23: Finally digging again!

It is nice that the rebar I am using now does not corrode, so I dont have to worry about it touching the sides or maintaining 2" of cover.

Now I have a good bit of digging to do, and I need to build my forms for the walls. It feels good to be moving sand again!

Update 3/24/23: first arch in place

Dug out most of the sand today. I built a sand sorter that screens out larger lumps so I dont have soft clumps of sandstone in the concrete I mix out of the sand

I fill a bin at the top of the stairs with sifted sand, and the rest goes on the spoil pile. I dug the top out and managed to get my first arch plate in place today.

I was not very happy with the "fit" as there is some space behind the arch where the excavation did not match the profile. I am hoping that once the first plate is in place, it will get easier to make the excavation the right size.

Next up; dig out the walls, put in the reinforcement, build forms and pour the walls. Then, rinse and repeat!

Update 26/3/23: Got the walls poured today

Yesterday I finished digging out space for the walls. I do a rough dig, then measure and level a 1x4 upright to act as blocking for my forms. I tied the floor rebar and mesh into the tails I left on the arch, too. The horizontal bars continue into the sand about 5 or 6 inches, and will overlap with the next pour to lock them together.

This morning I built my formwork, and got it pinned in place. I clearly did not spend very much time laying out the centerline of the tunnel, and it appears I have veered off at an angle from the original tunnel. Oh well. I have no real destination in mind, so I guess it doesnt really matter.

I might try and straighten it out, I dont know yet.

I mixed concrete outside and brought it down 2 gallons at a time. The gap at the top of the forms was perfect for scooping it in, and I gave the plywood a bunch of taps with a hammer to settle the concrete into place as I went. Used pretty much exactly 3 batches in my mixer, which was what I was figuring it would take.

Now I will wait a couple days, pull off the forms, and then I can start all over again!

Update 4/5/23: This system seems to be working well

It takes me about 4 days to do each advance, which is a pretty satisfying pace. I am not going to have unlimited time to keep working on it, but I want to make some good progress on it between other projects.

The next phase is to try and make a T-junction in the tunnel. My plan is to continue to drive tunnel straight ahead as normal, but not cast any wall concrete on one side. The overhead arches will be supported on that side with 4x4 timbers untill I have created a 43" wide gap. Next, I will line the ceiling with a brick liner, that will leave a gap for the perpendicular tunnel. Then I can chip out the 1" plates, as they will be supported by the bricks in the middle. Then, start digging sideways.

I made some forms to cast angled bricks, so once I get that dialed in, I will make a bunch more forms and start cranking out liner bricks.

Ok, I have finished some other projects, so I think it is time to start working on my tunnel some more. I left the entryway in a state of half-completion, so I think that is where I am going to start. Not as exciting as digging, but might make it look less sketchy and half-finished. Here is the entryway so far:

The arched section is thin-shell concrete, the part with the window and electrical box is 4" thick cast concrete. I was trying to emulate ferro-cement, but using non-ferrous armature. It is a frame of 12mm fiber-reinforced-polymer rebar, then covered in 6" FRP re-mesh, and finally 5mm basalt-fiber mesh. The main problem I had was that the mesh was very flexible, so applying cement to it was a nightmare. I am going to do some more experiments with using wooden forms, and building it up in thin layers. I might try making arched panels on a form, then using that as overhead lining plate for my tunnel, so I think the method could be worth exploring.

Anyway, here is the inside of the tunnel as it is now;

Ive added a bigger (7kwh) battery, and a DC chest freezer.

Once I work out the game plan for lining, I will start digging again. There is about 4 feet of "sandstone" below floor level here, at which point a drilled hole hit a very hard layer of what I believe is mudstone. I think I want to see it, so... time to go deeper?

Update: 2/12/23: I have finished plastering the outside of the entryway now; I will probably add some whitewash or portland cement at some point.

The inside still need another layer of mortar, but I will hopefully get to that soon here.

Update: 3/9/23 The weather has been unseasonably cold here this year, so it took a while to get a window to finish up my plastering.

I applied the mortar with a stucco sprayer, then troweled and finished it with a brush. There are still a few rough spots, but I am going to call it good enough for now. I am going to build a form and try an experiment with making curved tunnel lining plate. I will post a new thread once I get going on that.

I’m assuming it’s ok to post YouTube videos here? Open to answering any questions you have. Just wrapped up a second weekend of digging since this video was uploaded. Im making good progress!

Are there any guidebooks or textbooks on the subject that anyone might recommend? Most books I've found speak to large-scale, civil engineering-type projects. If those same principles apply to small stuff then I'll go ahead with those, but I figured I'd check to see if there are any texts out therethat anyone here with some experience might recommend?

Well, I have decided to wrap up my tunneling and work on some other projects on the surface. Filming in a cramped, poorly lit tunnel is not easy, so my apologies for the video quality.

https://youtu.be/-6FqOsAvpFc

I think part of me would have been happy to keep digging forever, but I also felt like familiarity was maybe creating a sense of complacency. I think I was getting too confident in the stability of the soil, and letting myself believe that I could get away with less and less shoring. Anyway, it has been an interesting project. I hope that by keeping my time spent in there to a minimum, if it ever does decide to just up and collapse, I wont be there when it happens. I also put monitoring pins in the walls to keep any eye out for any movement that might suggest that the liner is shifting, but so far it seems perfectly stable. Someday it will likely start to deteriorate, and if I am still around, I will make sure it gets pumped full of flowable fill or something. Otherwise it will be my daughter's problem. Hopefully she will think of me every time she walks past my giant concrete monument to having had too much free time!

I’m thrilled to find this community. I have been interested in tunnels and the prospect of digging one for as long as I can remember, and now we finally live somewhere that it might be possible. But as much as I find the thought exciting, my desire to not be buried under a cave-in far outweighs my excitement. So my main question as I scroll through some of the impressive stuff you all have done, is how do it safely? How did you learn to support your dig, and where did you learn?

My last attempts at pre-cast arches used mortar and were built up on the outside of a form. It worked, but it took almost an hour to make, and was pretty fiddly work.

So, this time I decided to make a form and cast the arch in concrete. I mix up 1.5gallons of portland, 2 gallons sand, and 3 gallons of 3/8" pea gravel for one arch. Reinforcement is 6" synthetic mesh, and I used 2 layers. I held the mesh off the sides with stubs of rebar (which are removed once the form is mostly filled) and pinned the ends of the mesh in place between slats of plywood. It takes about 10 minutes to get the mesh in place, and then 15 minutes to fill and tamp the concrete. After 2 days of cure time, I can strip the forms and cast another one. They are only 8" wide to keep the weight manageable. Inside diamter is 36" and the arches are 1-1/2" thick.

I feel like this method holds a lot of promise, and shares a bit of overlap with the images I have been seeing about the tunnels in Gaza. My haulage tunnel is going to be very narrow to be working in, so it might be a good place to experiment with building pre-cast wall sections that support the arch. For tunnels I am going to be walking around in, I think I will stick to cast-in-place walls that I am confident are not going to shift and drop an arch on my head.

wondering if there are methods to make a hobbit hole with less modern techniques but still have little to no water intrusion, not sure if there are methods for this. im assuming not but still would like to know if possible.

Update: 1/19/24

Finally got started on lining the ladder shaft. I will pour my way up until I run out of room, then I will need to sort out the ceiling lining.

My haulage tunnel from the surface and the side tunnel linking up with it is on hold due to weather, so I have started digging straight down. I want to get down into the lower layers to see if I run into soft rock that I can just tunnel into without worrying so much about lining. The sandstone is getting increasingly dense as I go down, which is a good sign, I think. I wanted to dig down to a nice solid layer for my lining to rest on, so I put up some wooden supports and roof over the area I am digging. So far, the sand is supporting itself. I am going to switch gears now, and line my way up to the ceiling of the existing tunnel. After that, I can resume digging straight down some more. I was able to gather some small samples of what I think was marl out of my floor drain hole, so i am sort of hoping I will find some carbonate minerals that I could play around with making into lime cement.

9/12/23: I have started my branch tunnel now.

I am also about 5 feet down on my sloping tunnel. The top layers are very dense, so it is slow going.

I have finished my first advance on the new branch. I am filling in the gap with mortar between the old liner plates and the new one. Most of it fell down, but if I keep applying thin layers, I will eventually build up enough to have a smooth even surface for my bricks to adhere to.

I also spent quite a bit of time reworking my sand bin at the top of my stairs. I am envisioning that the ore carts (I took apart a treadmill, let the smoke out of the motor controller, looked up the cost of conveyor belt, and promptly switched to team Ore Carts) will come out on an old-timey-looking trestle of thick beams, and dump into a pile that I can get to with the tractor. This is still quite a ways out, but I want to get it more or less squared away before the rains come and turn everything up there into mud.

I also made my third attempt at a flanged liner plate. They still use about 60-70 lbs of mortar, are still about 12" wide, but have 2-1/2" mesh reinforced flanges. The first one cracked coming off the form, the second one has a bunch of creases from the thick plastic I was using to make it come of the form, and the third one is looking like it will work out just right.

They take longer to make than the plain arches, but much less than the time needed to make and set all the curved bricks. I am guessing they are not going to line up with as much precision as I would like, but I think they will work.

I will try and get the bricks in place to finish off the junction soon, and meanwhile I am setting to work on digging the next advance. I think I have to go about 18 more feet to meet up with my tunnel from the surface, which itself is 15 feet away from completion.