Thx.
I personally would not expect such technologies to be buried in the actual soil.
In basements several stories down . . .
or abandoned mines or wells . . . But I don't think such 'tools' would be buried in any kind of typical ways. They are both too valuable and too dangerous.
I think quite the reverse. Buildings change hands, they get condemned or leveled for other reasons. Weather or other natural disaster will have a greater effect on a building than an object buried properly in soil. The key word is properly. I have training in creating a cache of firearms for use at a future time. Done correctly any modern firearm and it's ammo will be ready for use once unearthed and wiped clean of preservative grease and they will stay pristine buried in the soil for over 100 years. Done correctly. Screw the pooch even by a teeeeny amount and you'll uncover a heap of solid rust.
But today, I'm going to create caches by sealing my weapons and ammo inside heavy plastic or pvc pipes with waterproof, airtight seals at one or both ends. I'm going to emplace them in an area I will recognize many years away. I'll take two or more compass azimuths to confirm positioning. I may emplace it next to a railroad track or salt the area with many shards of dense metal to throw any sort of detectors off the scent. But, was this material for my survival cache readily (such that acquiring it wouldn't raise any suspicions) available in say the 1950's or 1960's when presumably the devices were emplaced? More importantly, was the supply sufficient to cache an object the size of a suitcase nuke from that era? I dunno. Remember the movie: "The Graduate?" What was the secret word offered by the wise older man to the young stud as the secret to future riches? One word: "Plastic."