Which soil classification is associated with well-graded clean sands and gravel-sand mixes?

The classification associated with well-graded clean sands and gravel-sand mixes is indeed denoted as SW, which stands for "Well-graded Sand." This classification system is part of the Unified Soil Classification System (USCS), which categorizes soils based on their grain size distribution and plasticity characteristics.

Well-graded clean sands are characterized by a good distribution of particle sizes, which enhances their compaction properties and overall stability. This means that when pressure is applied, the sand has a greater ability to resist movement, making it suitable for various construction applications, such as foundations and backfill. Similarly, gravel-sand mixes that are well-graded also exhibit these beneficial properties, combining the stability of gravel with the adaptability of sand.

In contrast, other classifications such as SP, which signifies "Poorly Graded Sand," would indicate a material with a limited range of particle sizes, potentially leading to issues with compaction and drainage. Similarly, the designations SM and GC describe sand with silt content and gravel with clay content, respectively, neither of which fit the description of well-graded clean sands or gravel-sand mixes as precisely as SW does. Therefore, SW accurately captures the characteristics of well-graded clean sands and gravel-sand mixes,