堆 (pile / heap) + 放 (place) - 'place in a pile'. Compare with the simpler 堆 ('to pile') which works alone, and with 摆放 ('to arrange / place neatly') - 堆放 emphasizes piling up rather than orderly placement.
usage
Often appears in safety / public-order contexts (warehouses, fire codes, neighborhood notices) - 堆放杂物 (piling up junk) is a common complaint. Construction and logistics use it for material stockpiles.
