R-value: Information and Much More from Answers.com

The R-Value test, California Test 301, measures the response of a compacted sample of soil or aggregate to a vertically applied pressure under specific conditions. This test is used by CalTrans for pavement design, replacing the California Bearing Ratio test. Many other agencies have adopted the California pavement design method, and specify R-Value testing for subgrade soils and road aggregates.

The test method states:

The R-value of a material is determined when the material is in a state of saturation such that water will be exuded from the compacted test specimen when a 16.8 kN load (2.07 MPa) is applied. Since it is not always possible to prepare a test specimen that will exude water at the specified load, it is necessary to test a series of specimens prepared at different moisture contents.

R-Value is used in pavement design, with the thickness of each layer dependent on the R-value of the layer below and the expected level of traffic loading, expressed as a Traffic Index. Details of the pavement design procedure are given in Chapter 600 of the California Highway Design Manual.

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Soils	Clay · Silt · Sand · Gravel · Peat
Soil properties	Hydraulic conductivity · Water content · Void ratio · Bulk density · Thixotropy · Reynolds' dilatancy · Angle of repose · Cohesion · Porosity · Permeability · Specific storage
Soil mechanics	Effective stress · Pore water pressure · Shear strength · Overburden pressure · Consolidation · Soil compaction · Soil classification · Shear wave
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Laboratory tests	Atterberg limits · California bearing ratio · Direct shear test · Hydrometer · Proctor compaction test · R-value · Sieve analysis · Triaxial shear test · Hydraulic conductivity tests · Water content tests
Foundations	Bearing capacity · Shallow foundation · Deep foundation · Dynamic load testing · Wave equation analysis · Crosshole sonic logging
Retaining walls	Lateral earth pressure · Mechanically stabilized earth · Soil nailing · Tieback · Gabion · Slurry wall
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