Underground working

Today (as of last visit 2021) any kind of underground work (especially in hard rock) is very time consuming and energy extensive. With APM technology this may change radically. Digging and cutting speeds that are form todays perspective astonishing should be possible.

Basic characteristics of advanced atomically precise diamondoid underground working systems

With APM technology one could make cutting saw-blades that:

• are made from superhard refractory diamondoid materials
• are only some micrometers thin giving them high surface area relative to their volume and thus good self cooling properties
• are actively cooled with capsule transport allowing for even faster cutting
• can transport away micro debris also employing capsule transport
• regularly replace their cutting teeth (self repair)
• are driven by shearing drives

With atomically precise diamondoid saw blade systems (many small scale blades) big sized chunks of soil (e.g. liter to cubic meter) could be cut out both carefully preserving their interior structure and fast because less material and thus less chemical bonds are broken. The then following transport to the surface can be made very energy efficient with infinitesimal bearing rails that are included in the wall sealing and support structure.

Dissolving and washout instead of or in conjunction with mechanical cutting

If the Underground work at hand is about excavation rather than resource utilization then one would probably only want to dissolve the very thin cutting planes not the whole volume of rock. This is orders of magnitude more energy efficient and can preserve the structure of the excavated bedrock for eventual later analysis.

Quite common calcite CaCO₃ rock is easily dissolvable with many acids.
When looking at this mineral as a salt (calcium-carbonate):
Both carbonates and calcites are usually on the more water-soluble side.

Most rock in Earth's crust is made up out of silicates and aluminates though which are either barely dissolvable or pretty much not at all dissolvable. When looking at these minerals as a salts:
Orthoisilicic acid and Orthoaluminic acid (aka aluminium hydroxide) are with a very few exceptions highly water-insoluble.

One way to solve this issue may be to shoot the cutting lines with an ion beam out of sodium ions. Because pretty much all salts of sodium are water soluble. Basically one converts the rock into a sufficiently ionic salt. One then can progress a "cut" with thin hot high pressure water-jets. In case water is squeezed as a liquid through a nozzle then the thinness of water jets is limited by water viscosity. This does not apply to levitated nano-droplets.

One of course could also try to use extreme acids that are known to dissolve quartz like e.g. hydrofluoric acid. But this seems much less practical given that fluorine is a much more rare element than sodium and also much more environmentally problematic.

Transport of sealed soil blocks

It's hard to have the block size almost equal to the digging channel size when the cuts are just micrometers thick and the blocks meters in size. For this to work the ground must be out of perfectly self supporting rock and the drill channel must have very consistent cross section. It could be like a bore hole with no or very low bending radius. Digging out just a bunch of almost perfect meter sized cubes and sliding them out through channels almost exactly the same size moving them along micrometer sharp 90° corners is probably impractical. The problem: full stops of motion at those turns due to the high inertial mass of the huge blocks and potential deformation of the blocks due to very thin hull and potentially unstable interior material. This can be limited to the initial straight move just after the cutting process when the cubes are made smaller than (e.g. one third the size of) the transport channel.

Preserving geological history stored in the lithosphere

Although the Lithosphere does not grow back in reasonable amounts of time like plants do today (2016) the lithosphere is one of the least protected things. Our current technology is just not powerful enough to endanger it. With advanced atomically precise technology this might drastically change. Doing future massive underground work as nondestructive as possible might become a very important aspect of the design of underground working systems. Underground work with minimized destructiveness basically amounts to cutting out blocks as big as possible and cutting them out with as thin as thin as possible cuts plus permanently tagging the cut out blocks and documenting where they came from allowing for later conduction of geological and planetary science.

Assuming a cut width of one micrometer and a core diameter or one meter (in square) the ratio between the preserved drill core volume and destroyed cut volume is:
(10⁶)²:1 or 10¹²:1 or 1 000 000 000 000 : 1 meaning that if you excavate one cubic kilometer of material you only irreversibly destroy the structure of one liter of material.

Usage of the gently excavated material

Beside preservation for later research the "drilling cores" can be stored as structural building material where maximum material strength is not of importance or as mass giving filler material in more sturdy and lighter diamondoid metamaterial building materials or in thinner slices as decorative pieces (e.g. diamond encased granite). If both the excavated volume and the built up volume isn't needed anymore the cores could be put back to their origin almost restoring the natural state of the lithosphere (of course on the very long term movements of the ground will complicate things).

Sidenote: There is a vague similarity to microcomponents.

Ultra-deep underground working - far term

A high amount of energy is only required for lifting stuff up from very great depths. a few hundred kilometers down the necessary energies are like the energies involved in spaceflight to LEO (low earth orbit). One don't has to propell the propellant and one can go slowly though.

[Todo: analyze what could be done if very hard rock like corundum (Al₂O₃) is encountered - Na⁺-ion beams? and slushing with water? see: diamondoid waste incineration ]

Related

• deep drilling
• specifics to tunnel construction (tunneling)
• specifics to near surface excavation work
• specifics to prospective work for mining (deep mining) - mining might decrease due to independence of scarce elements though
• geoengineering - (controlled tectonic tension release cables?)
• mining