Not much help and no text, but interesting. Build Your Own Basic Underground Shelter. Definitely not for a near-blast scenario, but a good enough temporary rabbit hole. Personally, I'd rather have room to roam. The Root Cellar Home Page.
Root cellars are nature's way of storing fruits and vegetables.
And they can be excellent storage areas for other things as well. A hundred years ago root cellars were one of the few ways they had of keeping things cool. People not only put potatoes and carrots in their root cellars, but their preserved meat, milk and cream, fruits and vegetables - literally anything they needed to keep cool. Even though root cellars didn't get nearly as cold as a refrigerator during summer months, root cellars generally were and are 30 to 40 degrees F cooler than daytime summer temperatures.