What characterizes Gap Graded Soils?

Gap graded soils are characterized by the absence of one or more particle size ranges within the soil sample. This means that there are certain sizes of particles that are not present, leading to a "gap" in the distribution of sizes. This can affect the engineering properties of the soil, such as its compaction behavior and drainage characteristics.

In gap-graded soils, the presence of various particle sizes that do not cover the entire spectrum can create specific voids, which may influence how these soils behave under load or when subjected to water flow. This can be particularly important in applications of soil mechanics and geotechnical engineering, where understanding the grading of soil can be critical for ensuring stability and proper foundation performance.

Other characteristics mentioned in the choices do not accurately describe gap-graded soils. For instance, a uniform distribution of all particle sizes refers to well-graded soils, which have a continuous range of sizes that contribute to a better packing and density. Similarly, the shape of the grains or the plasticity index may vary independently of whether the soil is gap graded, making those factors less relevant to the defining characteristic of gap-graded soils.