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Thus, soils are said to be compacteddry of optimum or wet of optimum (i.e. The water content of a compacted soil is expressed with reference to the OMC. The reason is that the values of the maximum and minimum dry densities (or void ratios) depend on the gradation and angularity of the soil grains. Where emax and emin are the maximum and minimum void ratios that can be determined from standard tests in the laboratory, and dmin anddmax are the respective minimum and maximum dry densities On the basis of relative density, sands and gravels can be grouped into different categories: Relative density (%) Classification 85 Very dense It is not possible to determine the dry density from the value of the relative density. If e is the current void ratio or d is the current dry density, the relative density is usually defined in percentage as For these soil types, it is usual to specify a magnitude of relative density (ID) that must be achieved. To achieve maximum dry density, they can be compacted either in a dry state or in a saturated state. However a large quantity of water is required in this method. The seepage force of water percolating through a cohesionless soil makes the soil grains occupy a more stable position.
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For compaction, application of vibrations is the most effective method. Plasticity of the soil Water content Compactive effort For cohesionless soils (or soils without any fines), the standard compaction tests are difficult to perform. Factors Affecting Compaction The factors that influence the achieved degree of compaction in the laboratory are:
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