What are the primary types of soil classification?

The primary types of soil classification are based on the soil's behavior and its engineering properties, particularly in relation to moisture content and how it responds under load. Cohesive soils are characterized by fine particles that stick together due to moisture, which is often seen in clay. Granular soils, on the other hand, consist of larger particles that do not exhibit cohesion, such as sand and gravel.

Focusing on cohesive soils, the term "coarse-grained" typically refers to soil types that are composed of larger particles. While the other options mention various types of soil, they either do not encompass the full spectrum of classifications or mix terms that aren't typically applied in this context, like limestone, which is a rock type rather than a soil classification.

Cohesive and granular significantly represent two broad categories that encompass major soil types, allowing engineers and geotechnical professionals to tailor their methods of testing and analysis to predict behavior under various conditions. This distinction is vital for construction projects, as it affects stability, drainage, and the overall integrity of structures being built.