Which backfill material can achieve maximum density with minimal compaction in a moisture-saturated condition?

The correct answer is that sand can achieve maximum density with minimal compaction in a moisture-saturated condition due to its particle size and cohesion properties.

In soil mechanics, sand is considered a granular material, which means it consists of larger particles that promote effective drainage and allow water to flow through. When sand is saturated with moisture, the individual sand grains can move and settle into a denser configuration more easily compared to finer materials. This property enables sand to achieve optimal density through the natural settling process when it is adequately moistened, requiring less mechanical compaction.

In contrast, clay has a high plasticity and finer particles, which tend to stick together. While clay can achieve density when compacted, it often requires more energy and time due to its cohesive nature and the role of water in influencing its compactability. Gravel, although capable of achieving good density, often needs proper drainage and specific moisture conditions to settle effectively. Lastly, silt contains finer particles that can retain water and may also require added compaction to achieve maximum density due to its cohesive properties, similar to clay, but with different behavior under varying moisture conditions.

Thus, sand stands out as the material that can efficiently reach maximum density with the least amount of additional compaction when