Which statement best describes the maximum soil lift thickness within the 6-12 inch range?

Which statement best describes the maximum soil lift thickness within the 6-12 inch range?

• A. 6 inches
• B. 8 inches
• C. 10 inches
• D. 12 inches

Answer: (D)

Lift thickness is about how much soil can be compacted effectively in one pass. When you’re working within a 6–12 inch range, you’re balancing how much material can densify uniformly with how much energy the equipment can apply. The upper end of that range—12 inches—is the maximum thickness that the compaction process can reliably handle while still achieving proper density and moisture distribution. Going thicker than that would risk poor compaction, voids, or uneven density. So, within this range, 12 inches is the best choice because it represents the greatest lift that can still be compacted effectively.

Lift thickness is about how much soil can be compacted effectively in one pass. When you’re working within a 6–12 inch range, you’re balancing how much material can densify uniformly with how much energy the equipment can apply. The upper end of that range—12 inches—is the maximum thickness that the compaction process can reliably handle while still achieving proper density and moisture distribution. Going thicker than that would risk poor compaction, voids, or uneven density. So, within this range, 12 inches is the best choice because it represents the greatest lift that can still be compacted effectively.