When placing and compacting backfill around structures in wet conditions, mechanical tampers are not permitted. Which material is required?

When placing and compacting backfill around structures in wet conditions, mechanical tampers are not permitted. Which material is required?

• A. Only A-3
• B. Only A-2
• C. Only A-5
• D. Only A-7

Answer: (A)

In wet backfill around structures, the goal is to have a material that remains workable when moist and can be compacted without the use of mechanical tampers, while still providing good drainage and support for the structure. The A-3 material is specified because it is a well-graded, free-draining granular fill that can be placed and compacted with manual methods, reducing pore-water pressure and the risk of damage to the structure. The other materials tend to have properties that either trap moisture or require vibration to achieve density, making them unsuitable when mechanical tampers aren’t allowed. Therefore, the A-3 material is the best fit for this situation.

In wet backfill around structures, the goal is to have a material that remains workable when moist and can be compacted without the use of mechanical tampers, while still providing good drainage and support for the structure. The A-3 material is specified because it is a well-graded, free-draining granular fill that can be placed and compacted with manual methods, reducing pore-water pressure and the risk of damage to the structure. The other materials tend to have properties that either trap moisture or require vibration to achieve density, making them unsuitable when mechanical tampers aren’t allowed. Therefore, the A-3 material is the best fit for this situation.