What kind of soils are often associated with high plasticity?

Soils with high plasticity are primarily associated with clays. Plasticity refers to the ability of soil to undergo deformation without breaking when force is applied. This property is crucial in geotechnical engineering as it determines how soil behaves under load and changes in moisture content. Clays, being fine-grained soils, contain significant amounts of minerals such as montmorillonite that contribute to their high plasticity.

When wet, clay soils can be molded and shaped, exhibiting noticeable changes in consistency and strength as moisture content varies. This behavior is essential when considering soil for construction, as high plasticity clays can lead to issues such as shrink-swell behavior, affecting foundations and structures.

Other soil types, like silts, sand, and gravel, do not typically exhibit the same level of plasticity as clays. Silts may have some plasticity but generally possess lower plasticity compared to clays. Sand is a coarse-grained soil that lacks the ability to hold water and does not exhibit plasticity. Gravel, similar to sand, consists of larger particles and typically behaves as non-plastic under various moisture conditions. Thus, clays are the predominant soil type associated with high plasticity, making them the correct answer.