What effect does high clay content have on soil?

High clay content increases plasticity in soil due to the unique properties of clay particles. Clay is composed of very fine particles that have a large surface area relative to their volume. When water is added to clay, the particles absorb it, creating a slurry that can easily be molded or shaped. This aspect of clay contributes significantly to its plasticity, which is the ability of soil to deform without cracking.

As a result, soils with a higher proportion of clay will exhibit greater plastic behavior during changes in moisture content compared to sandy or gravelly soils, which are more granular and less cohesive. This plasticity is essential in construction and geotechnical applications, as it influences how the soil will behave under load, how it can be compacted, and how it reacts with water, which can affect the overall stability of structures built on or within that soil.

In contrast, the other options highlight effects of soil properties that are inconsistent with the behavior of high clay content. For example, high clay content does not enhance drainage capability; rather, it can impede drainage because clay tends to retain water. Similarly, clay increases water retention rather than decreases it, and it certainly influences soil properties, making the notion of no effect on soil properties incorrect.