Thanks in advance!
You should just be able to click and drag where you want to dig the
tunnel. You have to make sure you've chosen the tunnel option in the
build menu and that you start right on one of the existing tunnel
walls. Some tunnels cannot be dug as there is impenetrable rock in the
way.
Jon S
from memory...
enter tunnel, select gruz, select tunnel type from defence menu, start
digging as you would build a bridge or dig a trench.
more 2150 stuff
http://earth2150.narod.ru/