Question

What is the cause of bulking in sand?

Answer 1

formation of sand dunes leads to bulking in sand

Answer 2

The volume of dry sand increases due to absorption of moisture. These volume increase is called  bulking of sand.

When dry sand comes in contact with moisture, a thin film is formed around the particles, which causes them to get apart from each other.

This results in increasing the volume of sand.Bulking of sand is primarily  depends on the moisture content and  bulking is directly proportional to  increases  of moisture.

It has been found that 4% moisture content (by weight) of dry sand may increase its volume up to 25 – 30% .