What type of soil is characterized as "C-type" soil?

C-type soil is classified as cohesive soil that has lower strength and stability compared to other soil types. It generally includes materials that can be more easily deformed, such as silts and clays, which are often moist. Specifically, clay soils fit into this category due to their fine particle size and plasticity when wet, which makes them less stable and more susceptible to movement when subjected to load or pressure.

Choosing sandy soil (80% sand) would not accurately represent C-type soil because sandy soil consists of larger particles and does not have the cohesive properties that define clay soils. Sandy soil tends to drain well and does not hold water in the same way that clay does, making it a distinctly different type of material when discussing stability and cohesiveness. Consequently, identifying C-type soil as clay soil aligns with its characteristics of being cohesive and potentially problematic in excavation or construction scenarios, fulfilling the criteria of what constitutes C-type soil under standard classifications.