Which classification corresponds to poorly graded clean gravels or gravel-sand mixes?

The classification that corresponds to poorly graded clean gravels or gravel-sand mixes is GP. This classification is part of the Unified Soil Classification System (USCS), which is used to identify and categorize soil types based on particular characteristics.

GP stands for poorly graded gravels and is specifically applied to gravels that do not have a wide range of particle sizes. These materials tend to be coarser and typically contain more larger particles compared to well-graded gravel, which would have a mixture of different sizes that can effectively fill voids and provide greater stability.

Understanding this classification is essential for soil engineers and geotechnical professionals because it influences how the material behaves under load and its suitability for construction projects. Poorly graded gravels often have higher permeability but may not provide the same level of compaction and interlocking as well-graded aggregates, making it crucial for designers to consider the implications of this classification in their work.