What is the designation for sandy soils mixed with non-plastic clay?

The designation for sandy soils mixed with non-plastic clay is indeed noted as SM-SC in the Unified Soil Classification System (USCS). This classification is used to identify and categorize soils based on their grain size and plasticity characteristics.

In the designation SM-SC, "SM" stands for "silty sand," which indicates the sandy texture of the soil mixed with silt and possibly some clay. The "SC" indicates "clayey sand," which suggests the presence of non-plastic clay within the sandy matrix. The combination reflects the soil's capability to drain well while also possessing some cohesive properties from the clay content, providing a useful understanding of how the soil will behave in various construction and environmental scenarios.

Recognizing the specific types of soil mixtures helps engineers and construction professionals in making informed decisions about soil management, compaction, and suitability for foundational support, which is critical for safe and effective construction practices.