Inorganic silts and clayey silts are classified under what designation?

Inorganic silts and clayey silts are classified under the designation ML according to the Unified Soil Classification System (USCS). The ML classification indicates that these soils possess plasticity and are composed primarily of silt-sized particles, which typically exhibit low to medium plasticity.

This designation is particularly important because it helps geotechnical engineers and soil scientists to understand the behavior of the soil under different conditions, including compaction, drainage, and shear strength. Knowing that a soil falls under the ML designation assists in predicting its engineering properties, which is crucial for construction and other civil engineering applications.

The other classifications mentioned—GM, GC, and SW—represent different soil types involving gravels and sands, and do not pertain to the silty classifications that are specifically described by ML. Thus, ML is the correct choice for identifying inorganic silts and clayey silts within the soil classification framework.