Since at least 1972 large nuclear powered Laser Tunneling Machines have been used to make Underground DUMB Tunnels.
I worked underground in those tunnels drilling and blasting from 1968 to 2010. The DUMBS were connected by Mag Lev Trains that traveled at Mach 2 speeds. The air was exhausted in the Shuttle Tubes so there was no wind resistance.
There are DUMB Tunnels under every major world city like Denver and Dallas Fort Worth. There are levels of cities in the tunnels as the earth’s crust is 800 miles thick. There are holes at the North and South Poles that you can see at night with the Northern and Southern Lights.
They melt rock at a billion degrees Kelvin and leave the tunnel walls (40+ in diameter) as smooth and hard as glass. The rock is vaporized so there is nothing to remove while tunneling as the machine advances at five plus miles a day.
The deeper ones were lazered down 6.2 miles or 10 kilometers and then a neutron bomb (without radiation) was sent down and detonated. That created a huge cavern from 10 miles to 30 miles in diameter.
The machines with multiple lasers were under US Patent 3693731 issued Sept. 26 1972 and US Patent 3885832 issued May 27 1975 for nuclear powered Laser Tunneling.
