This article shows three sizes of "underground" shelters, build using earth-bag construction (mostly).
http://theprepperproject.com/top-3-diy-survival-projects-save-life-coming-collapse/I would not call these "one-man" projects, but they could be built by just one person.
If you have a suitable bug out location, then take a look.
These are scalable and could be made into a community size project.
Several video are linked in the article and access to formal plans too.