How to Dig Tunnels

Dig a vertical shaft as there must be enough earth above a tunnel to allow for it to be walked on from above without collapsing. The distance between the roof of the tunnel and the surface of the earth should be twice the height of the tunnel to be dug. For a comfortable environment to work in, give the tunnel a width of around two feet and a height of two to two and a half feet. This size is also stable and unlikely to collapse (as opposed to larger tunnels).

Dig a vertical shaft of at least six feet in depth, if following the dimensions of the tunnel in Step 1. Seven to eight feet deep is, of course, a safer distance. Make the shaft larger than the tunnel's width for getting supplies in and out of the tunnel -- around three square feet. At a point in the digging process it will be easier to use buckets to haul dirt out of the tunnels than to throw it. Tie a long piece of rope to a bucket and string the rope over a piece of wood or similar object at the top of the vertical shaft to haul the dirt out.

Use a lump hammer, chisel or trowel to dig when digging outside of the vertical shaft and inside of the tunnels; a shovel will no longer be useful at this point due to size constraints. Use a pick to dig if the ground you are digging is too solid or contains a lot of rock.

Install shoring as you dig to make the process of tunneling safer. The spacing between shoring largely depends on the ground you are digging through and where it is relative to other tunnels. Denser ground will require less shoring, though erring on the side of safety is wise.

Cut one piece of timber to the width of your tunnel. Shoring timber should consist of 2 inch by 4 inch or 3 inch by 3 inch pieces of timber and 3/4 inch sheets of plywood. Secure the first piece you cut between two pieces of timber cut to the height of your tunnel minus the height of the first cut piece. When secured together by nails or screws, the shoring will form a "U" shape (which would be flipped to an "n" shape in the tunnel.) Construct shoring outside of the tunnels and then bring them in.

Secure plywood board between shoring posts placed approximately two to three feet apart. Place the sheets and braces as necessary throughout the tunnel. In ground which is crumbling, it is a good idea to complete the shape of the timber pieces from a "U" to a square and place plywood boards on the sides of the tunnel as well.

Install an air pipe before your tunnel gets too long. Use a flexible piece of piping at least one inch in diameter, cut with a knife to prevent the creation of bits of plastic, running from the entrance of the tunnel to along the sides or floor of the tunnel. Place a fan to push air through the pipe at the entrance of the tunnel.