I have in mind a world where a small colony of humans are isolated within a cylindrical force field in a desolate land of clay. With no tools their only option is to dig and, upon finding food (presumably some sort of dry desert tuber), they keep digging.
I would like this to go on for some generations, as the lack of ability to make permanent structures due to clay being their only building material (with limited rainfall), presents a lack of permanency that would result in these people losing any notion of culture or ambition, only the 'tradition' of digging. An interesting place to start with a protagonist that potentially finds a way out of the field.
This obviously puts constraints on how small this colony could be and thus cylindrical field must be - but the big constraint is what they can do with their waste clay as they dig, as well as their own waste.
My idea is that the walls of the force field could violently react with mass that touches it, sublimating it, with the mass being carried away as gas. The reaction could also provide a light source for the colonies when they are deep into the earth too.
My question is is this a feasible process? Is there a better way a colony could dispose of waste in this isolated system? And also is the current solution too deus ex machina?