Which preposition to use with scrunch

under Occurrences 2%

The ground seemed to be plentifully strewn with ashes, which scrunched under their feet as they plodded along, and their voices sounded hollow and strange.

against Occurrences 1%

As you have scrunched against the shelf not to block the passage, but with your head thrown back to see the titles up above, you have noticed at the corner of your eyeunless it was one of your blinder moments when you were fixed wholly on the shelfa man in a slightly faded overcoat of mixed black and white, a man just past the nimbleness of youth, whose head is plucked of its full commodity of hair.

Which preposition to use with  scrunch