Have you guys heard of these?  I was researching mining and extraction methods yesterday and discovered this gem.

Apparently, someone United States government (military?) scientists developed a nuclear powered machine that bores 40 foot tunnels at 7 miles per day without producing the normal 'muck' that has to be removed from the shaft.  They patented it in the early 70's, and there have been no other credible mentions since.  However, there are reports of 'whistleblower' construction workers who claim there are miles and miles of underground (2+ mi underground) tunnels connected by high-speed train between military bases.

Here are some links if you're interested in diving into this conspiracy:

http://projectcamelot.org/la5354ms.pdf

http://www.liveleak.com/view?i=c06_1362167820

http://www.thetruthdenied.com/news/2012/12/14/deep-underground-military-base-d-u-m-b/