Shipping containers as underground bunkers

I know I can't just get a container from ebay and bury it in a field. They're just not made to have mud dumped on top of them. But would it be possible to make a roof for a shipping container which puts the weight of the mud through the corners? When stacked, the weight goes through the corners of the boxes because that's where they are strongest. In theory a roof should make it possible to use a shipping container without the roof collapsing, and it would be a lot cheaper than building something for the task.