One of the projects that researchers at Los Alamos have worked on is a 'subterrene'. This is a nuclear-powered tunneling machine capable of boring through solid rock at high speed by melting the rock. They were granted a patent (No. 3,693,731) for this in 1972.
There's some info about this (as well as it's possible use on the Moon or Mars) in the book Terraforming Mars
A means, however, of generating a glass coating on the wall, as a direct result of the tunneling process could be achieved by nuclear heating and melting, rather than nuclear explosive crushing. This latter idea has been explored at the Los Alamos National Laboratory under the guise of the SUBTERRENE program in which it was envisioned that the heat from a fission-reactor might be used to literally melt the rock around it - effectively, that is, tunnelling by the controlled use of a China-Syndrome meltdown. Indeed, a US patent (#3,693,731) for such a nuclear tunneling machine, was awarded to Dale Armstrong and co-workers at Los Alamos in September 1972. The patent application states, "this invention provides a rapid versatile economical method of deep-earth excavation, tunneling shaft sinking which offers solutions to ecological problems, acquiring natural resources presently inaccessible and access to an enormous reservoir of natural heat energy. These valuable subterranean sources include natural minerals and hydrocarbons, fresh water and clean geothermal heat energy".
Wikipedia has an article about the Subterrene
The same technology was proposed by Joseph Neudecker and co-workers, in 1986, as a means by which tunnels might be bored upon the Moon in order to construct a subsurface transportation system. Describing their nuclear-powered melting machine as a SUBSELENE, Neudecker et al. calculate that a fission-reactor-heated, 5-m diameter tunneler could be made to advance by as much as a 50-m per day through the lunar subsurface. This tunneling, they argued could (indeed, must) be operated remotely. Importantly, for tunnel coherence and stability, the material melted at the front of the SUBSELENE would be extruded at its backend to form a glass lining on the tunnel wall.
, noting the rumor that the Soviets actually built such a device which they called the "battle mole".