From the Super Mario Wiki
Sand Piles are found only in the 50m level in the original Donkey Kong. They are on the multiple Conveyor Belts that are in the level, and if Mario touches one, he loses a life. The only way to destroy a Sand Pile is to use a Hammer.
Donkey Kong (Game Boy)
In the Game Boy game, Sand Piles appear only in the remake of 50m.