Which of the following is not a factor in determining the number of soil compaction passes required?

• A. Amount of compaction required
• B. Final layer thickness
• C. Initial soil density
• D. Moisture content

Answer: (C)

In soil compaction, the plan for how many passes to make centers on reaching a target density efficiently. The key factors are how much compaction you need to achieve (the required density relative to dry density), how thick each lift will be (final layer thickness), and the moisture content, which greatly affects how well the soil compacts and how many passes are needed to reach the target. The initial density you start with isn’t used to set the number of passes. It’s your goal density, the lift thickness, and the moisture conditions that drive how many passes you’ll run to arrive at the desired compaction across the area. If the moisture is near optimum and the lift is appropriately sized, you may achieve the target with fewer passes; if moisture is off or the lift is thicker, more passes may be required.