What is the most energy-efficient way to crush the hardest bedrock on earth while assuming it is impossible to use the chain reaction energy from that bedrock?
How many energy is needed?
TBM's are the acceptable methods for creating tunnels. I think they will not be able to work if you have bedrock made out of diamonds and it may be extremely slow if it were made out of corrundum. Personally I have never heard of any bedrock made entirely out of one mineral, hence the term bed"rock". As far as crushing rock any rock crusher will do the job. Most I have seen and used feed vertically into a pair of vice-like jaws with one jaw moving back and forth. Softer rocks like limestone will be crushed down as small as you want it. Other rocks are submitted to a test called an LA ware where the sample is beat with 8 steel balls in a rotating drum. After a certain number of cycles you measure the amount of material lost. Believe it or not Quartzite used as railroad ballast disintegrates in an La ware test.