What characterizes a soil sample that is uniformly graded?

A uniformly graded soil sample is characterized by nearly identical particle sizes. This means that the soil composition lacks a wide range of different particle diameters; instead, the majority of the particles are similar in size. This uniformity affects the soil's physical properties, such as permeability and compaction, making it behave in a predictable manner under load.

In contrast, a soil sample with varied or multiple particle sizes would be considered well-graded or poorly graded, depending on the distribution and range of sizes present. Such diversity in particle size can lead to changes in density and void spaces within the soil, causing it to behave differently than a uniformly graded sample. Therefore, the uniqueness of a uniformly graded soil is its homogeneity in particle size, which distinctly supports its classification.