D Value

A value which is used to indicate that a certain amount, as a percentage, of particles have passed through a stated sieve size. For example, a D value of D25 for a sieve size of 0.5mm, means that 25% of the soil sample would pass through a sieve size of 0.5mm (500 microns), with the remaining 75% being retained in the sieve. To determine the central value for the particle diameter of a sample, a value of D50 is used. The D Value is frequently used to determine the Gradation Index of a soil.