This spreadsheet estimates the subgrade Resilient Modulus from other commonly known soil data values for either cohesive or granular soils. The estimated resilient modulus can then be used in an AASHTO flexible road design program such as AASHTO Structural Design.
Some studies have shown that a reasonable correlation can be made between the subgrade Resilient Modulus value as used in AASHTO design guidelines, and other more common geotechnical parameters.
These soil details may already be known from previous site investigations or can be reasonably estimated at the preliminary design phase. Therefore, together with an AASHTO design program, this spreadsheet allows a detailed preliminary design to be undertaken before detailed site investigation works have been completed on the site.