Soils Grain Size Distribution

[Sebast_U_1973]

D₆₀ - D₁₀ are common parameters to work with from a Grain Size Distribution.
I am on a project which specifies a D₈₀-D₃₀ classification of the particle size.

What use would the D₈₀-D₃₀ have over the D₆₀-D₁₀ ?

Or has anyone come across this grain size distribution before ?

The project involves an Athletic field.

 

[Sebast_U_1973]

In addition to the above post, the following expresses the question with more detail:

Usually Sieve Analysis and material gradations reference the D₆₀ particle size and the D₁₀ particle size in order to obtain the C_u (Coefficient of uniformity) and also the D₃₀ is used in a formula for the C_c (Coefficient of curvature). So I was surprised to see a specification referencing the D₈₀, which in general would be smaller particles. (Comparing the same soil sample). Therefore, my question is what soil properties would this fraction of smaller particle sizes effect. Given a soil description of Silty Sand (USCS designation of SM). Would more smaller particle sizes effect the shrinkage factor, writer believes it would, aside from this property or behavior, this writer was searching for more definitive reasoning or output.

Any and all input is appreciated and look forward to summarizing a better conclusion on why this particular specification has referenced the particle size (D₈₀). Thank you for your time.