When studying different types of soils, it's important to understand their origin and properties. Aeolian soil is a specific type of soil, and its characteristics are directly related to how it is formed. Let's examine the given statements about aeolian soil.

Aeolian Soil: Definition and Formation

The term "aeolian" (sometimes spelled "eolian") comes from Aeolus, the Greek god of wind. This immediately tells us about the primary mechanism responsible for the formation and transportation of these soils.

• Statement B: The soil is deposited by wind.

  This statement is absolutely correct. Aeolian soils are formed when sediments, like sand, silt, and sometimes clay particles, are picked up, transported, and then deposited by wind. Examples include sand dunes found in deserts and loess deposits, which are vast accumulations of wind-blown silt.

Permeability of Aeolian Soils

Permeability is a measure of how easily water can flow through a soil. It depends on factors like particle size, void ratio (the volume of voids to the volume of solids), and the interconnectedness of pores.

• Statement C: The soil has large permeability.

  This statement is generally correct for aeolian soils. Here's why:

  • Wind-blown sands: Sand particles are relatively large, and when deposited by wind, they often form a loose structure with large, interconnected void spaces. This allows water to pass through very easily, resulting in high permeability.
  • Loess (wind-blown silt): While silt particles are smaller than sand, loess often exhibits a unique, open, cellular structure due to the way it is deposited and sometimes weakly cemented. This structure can lead to surprisingly high vertical permeability compared to other fine-grained soils like clays, even though its particle size is fine. However, upon wetting and collapse, its permeability can decrease. In its undisturbed state, it typically has higher permeability than many other fine-grained soils.

  Therefore, compared to many other soil types, especially clays, aeolian soils generally tend to have large permeability.

Density and Compressibility of Aeolian Soils

Soil density refers to how compact the soil is, while compressibility refers to how much a soil will reduce in volume under pressure.

• Statement A: The soil has low density and low compressibility.

  Let's break this down:

  • Low density: Due to wind deposition, aeolian soils are often deposited in a very loose state with a high void ratio. This means they contain a large volume of air-filled spaces. A high void ratio translates to a relatively low dry density. So, the "low density" part of the statement is often correct.
  • Low compressibility: This part of the statement is generally incorrect. Because aeolian soils (especially loess) are often loosely packed and have a high void ratio, they are typically highly compressible. When subjected to load or, particularly for loess, when saturated with water, their loose structure can collapse, leading to significant volume reduction (settlement). This makes them problematic for foundations. Therefore, describing them as having "low compressibility" is inaccurate.

  Since a part of statement A (low compressibility) is incorrect, the entire statement A is considered incorrect.

Conclusion on Correct Statements

Based on the detailed analysis of each statement:

• Statement A is incorrect because aeolian soils are typically highly compressible, not low compressible.
• Statement B is correct because aeolian soils are indeed deposited by wind.
• Statement C is correct because aeolian soils generally have large permeability.

Therefore, the correct statements are B and C.