Sometimes, a project simply demands that you do something the hard way (not the cheap way) and using a tool or piece of equipment in a way that God didn't intend it to be used... as is the case with burying a shipping container.  The sides weren't designed to take the constant weight and pressure, and the top surely can't support disbursed weight for extended periods of time.  That being said, if you simply must bury the container the safest way to do it is to used Gabion cages as external supports to carry the pressure of the compacted ground.

Why on earth would you want to bury a shipping container?

• Storm shelters
• Survival bunker
• Fall out facility
• Root cellar
• In-laws quarters
• Super secure man cave
• ... the list goes on, you can use your imagination...

Anyway, here's an article on the safest way to do it. Read more here.