What does a well-graded soil imply about its particle size distribution?

A well-graded soil indicates a continuous range of varying particle sizes that allows for efficient packing and minimal void spaces. This characteristic means that the soil contains a mix of fine, medium, and coarse particles, which together create a denser mass.

When soil is well-graded, it benefits from enhanced mechanical interlocking and increased stability, making it suitable for various engineering applications, such as foundation support and embankment construction. The presence of varied particle sizes can help in improving compaction and reducing the likelihood of settlement.

In contrast, the other options do not accurately describe well-graded soils. A narrow range of sizes indicates poorly graded or uniformly graded soils, which do not provide the same benefits as well-graded soils. Similarly, poorly sorted soils refer to mixtures where particle sizes are not evenly distributed, again contrary to the concept of well-graded soils. Finally, while plasticity can be a property of some soils, it is not a definitive characteristic of well-graded soils; plasticity relates more to the soil's ability to deform without cracking rather than its gradation.