How can I contain unexpected bottle bombs

Avoid it as previous answers have stated. Outside of that, if you are worried about it I would just condition in rubbermaid containers, mainly to contain the mess.

That said, I've never had a bomb, so i don't worry about it. I have had gushers though; mainly because I had a few too many homebrews while bottling my homebrew, and I doubled the priming sugar.

No matter how careful you are, you can pick up a wild yeast infection and wind up w/ gushers and bottle bombs. They do explode w/ some force--enough to cause minor injuries for sure--but a regular plastic storage container would contain it. I think the worst you would see is the glass exploding w/ enough force to damage the container but it would still contain the glass--but I've never had even that happen. Cardboard will too... but that's not so fun when you find the cardboard box that's been soaked in beer for three weeks.

In practice, the only precaution I take against bottle bombs is I sample the beer regularly for the first month or two. If it starts to gush, I put it in the fridge and drink it right away. Bottle bombs start out as just severely overcarbonated beer, if you catch it at that point, you should be pretty safe. Even safer is just to dump the beer.

The best way to avoid a "bottle bomb" is to ferment the brew to completion and then add a known amount of priming sugar before bottling. In such a way the amount of carbonation can be relatively well controlled and the "bomb" situation should never occur.

Some do not like using priming sugar and aim to bottle the beer before fermentation of the malt is complete. If the SG is checked to make sure the brew is in a suitable state then the carbonation should be predictable, after all "natural carbonation" should be a repeatable process to be useful.

However if the brew is repeatedly unpredictable or the brew is new and unfamiliar (eg "real" Ginger beer!) then the best thing to do is to use PET bottles with screw tops of the type used for fizzy drinks. PET bottles take a very high pressure and deform and burst rather than explode with "hard shrapnel" Using PET bottles allows one to experiment more safely and work out what conditions are needed to condition the brew safely in a glass bottle.

For my own experience and comments from other brewers I have noticed that "flip top" bottles rarely explode. It seems as the pressure increases the top is unseated and the excess pressure vents slowly. The wire retainer has some slight give and the rubber washer allows a good seal to be reformed after venting. So that may be a option with an inbuilt safety valve. YMMV

It is usually possible to use an enclosed style of plastic beer crate as a container for "highly pressurised" bottles. If there was a bottle explosion then the plastic crate walls would normally contain the flying shards of glass. But this is a false safety. Say the bottles were stored in such a crate or any other bin, barrel or container. Say they were highly pressured and just on the edge of blowing. That would be a very dangerous situation. For example, one might take a bottle from the "safe storage" and it may blow there and then in the hand due to the disturbance. No bin would prevent injury from an event like that. Which is why I recommend finding a way not to make a bottle bomb and if all else fails don't use glass.If one really must use glass try wrapping the bottles in industrial strength cling film. Even several layers of normal domestic cling film (or waterproof tape) will help stop or slow flying shards of glass.

Stay safe!