Which factor is crucial for determining the compaction of soil backfill?

All of the factors listed play a significant role in determining the compaction of soil backfill. Specifically, soil moisture content is essential because it affects the cohesive properties of the soil particles. Adequate moisture can help the particles bind together more effectively, enhancing the overall density of the compacted soil. Conversely, too much moisture can lead to decreased compaction and increased risk of soil instability.

The type of soil is also a critical factor because different soil types have varying properties that influence how well they can be compacted. For example, granular soils generally compact more efficiently than cohesive soils due to differences in particle size and shape.

Lastly, the compaction equipment used can greatly impact the compaction process. Different types of compaction equipment (such as sheepsfoot rollers, vibratory plate compactors, etc.) are suited for particular soil types and moisture conditions. Each piece of equipment has unique operational characteristics and effectiveness that can influence the achieved density of the backfill.

Since each of these factors is interconnected and contributes to the overall performance of the backfill during construction, recognizing their combined importance leads to the conclusion that all are crucial for determining the compaction of soil backfill.