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Plasticity index: 6 max N.P. 10 max 10 max 11 min 11 min 10 max 10 max 11 min 11 min 1: Usual types of significant constituent materials stone fragments, gravel and sand fine sand silty or clayey gravel and sand silty soils clayey soils General rating as a subgrade excellent to good fair to poor
The plasticity index is the size of the range of water contents where the soil exhibits plastic properties. The PI is the difference between the liquid and plastic limits (PI = LL-PL). Soils with a high PI tend to be clay, those with a lower PI tend to be silt, and those with a PI of 0 (non-plastic) tend to have little or no silt or clay.
The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil.The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol.
The present serviceability index (PSI) is a pavement performance measure.Introduced by the American Association of State Highway and Transportation Officials (AASHTO), the PSI is one of the most widely used pavement performance indicators after pavement condition index (PCI) and international roughness index (IRI).
Soil texture triangle showing the USDA classification system based on grain size Map of global soil regions from the USDA. For soil resources, experience has shown that a natural system approach to classification, i.e. grouping soils by their intrinsic property (soil morphology), behaviour, or genesis, results in classes that can be interpreted for many diverse uses.
The A-Line on the chart separates clays (given the USCS symbol C) from silts (given the symbol M). LL=50% separates high plasticity soils (given the modifier symbol H) from low plasticity soils (given the modifier symbol L). A soil that plots above the A-line and has LL>50% would, for example, be classified as CH.
Public Safety Standards, United States (Federal Government) – Offers free downloads of documents, including AASHTO's "A Policy on Design Standards", that have been incorporated by reference into the US Code of Federal Regulations and can therefore be freely copied as edicts of government.
The American Association of State Highway and Transportation Officials (AASHTO) is a standards setting body which publishes specifications, test protocols, and guidelines that are used in highway design and construction throughout the United States. Despite its name, the association represents not only highways but air, rail, water, and public ...