Soft wood trees, like the silver maples I have, as they get older have roots that break the ground surface. Adding top soil is only a temporary fix, as the roots will eventually surface again. While it is generally not a good idea to damage /destroy a tree roots, the silver maple is the next thing to a weed. I have routinely cut out the root segment that surfaces from my silver maple for decades. If your trees are silver maples, get out your axe and shovel and pull that root like a bad tooth.