the preferred compaction technique is ___ ___, and compaction should be done in small __

• A. Vibratory tamping, lifts
• B. Hand tamping, lifts
• C. Vibratory tampering, lifts
• D. Vibratory tampering, layers

Answer: (C)

Achieving proper backfill density relies on using a vibratory tamping action to densify the soil, not just static pressure. The vibration helps soil particles rearrange more tightly, closing voids and increasing dry density more efficiently than hand or static tamping alone. Doing this in small lifts is essential because each thin layer can consolidate evenly before the next is added, preventing deep zones of un-compacted material and reducing the risk of uneven settlement. Hand tamping tends to be slower and often doesn’t reach the same density for larger fills, making it less practical for consistent, efficient compaction. So the preferred approach is vibratory tamping across small lifts.