I made my tunnel with a chimney flue ,you can put several together they will not collapse , and fill over it to make a mountain with dirt or rocks .
Ben
Ray Dunakin wrote:Here's how I build my tunnels: First I level the area where the tunnel will be. Then I build up the walls of the tunnel out of concrete bricks. Next I add some dirt to the inside of the tunnel to build up the grade to the proper angle. After laying the track, I cover the top of the tunnel with concrete slabs about 1.5" to 2" thick. Then I build my mountain over it.
Tom Trigg
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