Sand could, as well as any other type of soil. If the sand moves down relative to the pile, the shear resistance developed will be in the negative direction (downward). If the positive direction shear resistance in the soils further down is insufficient to resist this load, the pile can be dragged down, Hence, "downdrag". If the pile is not dragged down, the pile will be subjected to dragload. Previous comments in Discussion Forum have elaborated at some length on the problem (and associated definitions). Use the keywords to search the Forum and you will find several comments of interest covering the topic.