Relative Density (Density Index) of a Cohesionless Soil

Where a Proctor curve is poorly defined and relative compaction is the wrong spec. Dr = (e_max - e)/(e_max - e_min) on void ratios; substituting e = Gs gamma_w/gamma_d - 1 cancels the specific gravity and the unit weight of water entirely, leaving Dr = gamma_d,max (gamma_d - gamma_d,min)/(gamma_d (gamma_d,max - gamma_d,min)) - which is why no Gs is asked for. A field density of 117.6 pcf at 12% moisture is 105.0 pcf dry, and against index densities of 90 and 115 pcf that is 65.7%. Dr is measured against the LOOSEST and DENSEST index densities of that same soil, not a Proctor maximum, so the two scales are not interchangeable: a sand at 95% relative compaction can still be loose. Outside 0-100% means the field density falls outside the index-test range. A QC aid; the project geotechnical specification and the testing agency govern.

gamma_d = gamma_wet/(1 + w/100); Dr = 100 x gamma_d,max (gamma_d - gamma_d,min) / (gamma_d (gamma_d,max - gamma_d,min)), the dry-density reduction of Dr = (e_max - e)/(e_max - e_min).

Relative density (density index) as defined on void ratios and reduced to its dry-density form, standard soil-mechanics practice as compiled in Das, Principles of Geotechnical Engineering, and NAVFAC DM-7.01; the minimum and maximum index dry densities come from the laboratory index-density tests for that soil and are entered by the user.

The definition and its dry-density reduction are public first-principles soil mechanics; the reduction is shown in the note so it can be checked by hand.

Estimate. AHJ and licensed professional govern.

Field names used by the API: field_wet_pcf, w_pct, gamma_dmin_pcf, gamma_dmax_pcf, gd_field_pcf, dr_pct

• Definition Dr = (e_max - e)/(e_max - e_min), reduced to the dry-density form; Gs and gamma_w cancelsoil-mechanics first principles
• Index densities entered the minimum and maximum index dry densities are laboratory results for that soil, entered by the userlaboratory index-density tests
• Not relative compaction referenced to loosest/densest index densities, not a Proctor maximum; the scales are not interchangeableDas / NAVFAC DM-7.01
• Descriptive bands very loose / loose / medium dense / dense / very dense are conventional terms, not a code requirementcommon professional usage