If soil density increases while water content remains constant, what happens to porosity?

If soil density increases while water content remains constant, what happens to porosity?

• A. Increases
• B. Decreases
• C. Stays the same
• D. Becomes irrelevant

Answer: (B)

Porosity is the fraction of a soil’s volume that is empty space, which can hold air or water. When density goes up due to compaction, more solid material fits into the same volume, so the void spaces shrink. Since porosity measures those voids, it decreases. The water content staying constant doesn’t create more void space; it just means the same amount of water relative to the dry soil is present, but there is less space to hold it. So increasing density while keeping water content constant reduces porosity.

Porosity is the fraction of a soil’s volume that is empty space, which can hold air or water. When density goes up due to compaction, more solid material fits into the same volume, so the void spaces shrink. Since porosity measures those voids, it decreases. The water content staying constant doesn’t create more void space; it just means the same amount of water relative to the dry soil is present, but there is less space to hold it. So increasing density while keeping water content constant reduces porosity.