mound up
To pile something together into a mound. A noun or pronoun can be used between "mound" and "up." We mounded up all the debris we could find for the bonfire later that evening. Don't just mound the grass clippings up in the corner of the yard like that—they'll start stinking up the place!
mound something up
to form something into a mound. Mound the dirt up around the base of the shrub. Please mound up the leaves around the rosebushes.