Unified Soil Classification System Wikipedia
Unified Soil Classification System. If the soil has 5–12% by weight of fines passing a #200 sieve (5% < P #200 < 12%), both grain size distribution and plasticity have a significant effect on the engineering properties of the soil, and dual notation may be used for the group symbol. For example, GWGM corresponds to "wellgraded gravel with silt ."...