>>274784139
Shipping containers are made of metal. They corrode really fast when in contact with water and soil. Oh you might be thinking why not just cover it with plastic or something! Even plastic will get eventually destroyed by things living in that ground.

Though there hasn't been a practical test on this yet. I'll have to check this. Since the container can hold like 55,000 lbs of weight over its 20ftx8ft floor area = 0.35kips/sqft . The walls are similar in strength as well. 

See Passive soil pressure with EQ load.
I'll simplify calculations since I'll be sleeping soon.

To be able to make a VRbunker using a Container the container walls must be able to withstand about 4 kips/sqft of pressure. That's about 4000lbsx(20x8ft) = 640,000lbs of load all over the wall.
So sorry it's impossible. You need stronger walls mate.


TLDR;
Container wall strength capacity = 0.35kips/sqft
Passive Soil Earthpressure+EQ = 4kips/sqft