Relative Quality of Roadbed Soil
Iowa Soil Type CBR Resilient Modulus, psi Effective Resilient Modulus, psi Information Icon k-value (psi/in) Losss of Support k-value (psi/in)

Select 7 8,877 6,776 Information Iconnformation Information Iconnformation
Suitable 5 7,157 5,482
Unsuitable 3 5,161 3,965
*For resilient modulus calculation, the following equation was used:
Resilient Modulus Equation
From: Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures, APPENDIX GG-1 pg. GG 1.52
*For stabilized soils, the following equations are used to characterize the material
Resilient Modulus Equation for Stabilized Soil *This equation is solved for Mr
Mr fly ash = 17,500 psi
*Effective Modulus of Subgrade Reaction, psi/in
k = Mr/19.4
Soil quality in Iowa