Shipping containers buried with no retaining walls around them fail very quickly. The strength in containers is in the frame not the sides so they collapse with the weight of the soil, one of the US tv shows on how things work did a demo. On the grander scale of bunkers my wife and I were watching a show about the Mormons in the US who due to their polygamous family ethic lived in a remote part of the country. They had blasted out large caves in the hillside, it looked like red sandstone, and created lovely homes. Obviously natural light only came in the front windows but great idea. The 'hobbit houses' on Harris are lovely looking, facing a great westerly storm in one must just be beautiful. There's another one in the vicinity of Arisaig near Mallaig built in a cliff if I remember really breathtaking.
I spoke to a few old guys in the ROC and they knew that past the initial few reports they were a goner. I've spent quite a bit of time in and around well functioning MOD bunkers, one built under the casino of the Rock Hotel in Gib. At one large complex I worked in they used to practice 'lock downs' in the 1980's. As the oncoming watch came on, close down the doors and keep it shut for 24 - 48 hrs. Apparently it tested, catering, accommodation, patience and good will. The accommodation was wire frame bedsteads bolted to the wall in the pipe tunnels they were 2 - 3 high. By the time I was there the mattresses had all been removed as a fire hazard. We used to joke about suspicious orders like 'bring your mattress on watch with you' 'Why you ask? No reason and are you aware of the benefits of the common pillow?'. Lets face it once the melty face nukes have hit or the nerve/biological agent has effectively created a desert what fun are you going to have underneath the ground. As a man cave or weekend retreat in the woods though, love it.