Which soil type is indicated by the symbol 'GC'?

• A. Clayey-gravels
• B. Organic silt
• C. Poorly graded sand
• D. Silts

Answer: (A)

The symbol 'GC' refers to clayey gravels in the Unified Soil Classification System (USCS). This classification is defined based on a combination of the soil's grain size and its plasticity characteristics.

In this system, 'G' stands for gravel, which indicates that the majority of the soil contains particles larger than 2 mm. The 'C' signifies that there is a substantial amount of clay present within the gravel matrix. This combination affects the soil's behavior, strength, and drainage properties.

Understanding soil classifications is essential in engineering and construction, as it helps determine appropriate methods for excavation, construction, and the overall stability of the soil when subjected to loads. By identifying 'GC' as clayey gravels, one can anticipate properties such as increased plasticity and potential for swelling or shrinkage when moisture conditions change, which can significantly impact construction practices.