Bearing Ratio (CBR). Common equations using CBR to calculate resilient modulus
values include the following:
E (lb/in2) 1500 CBR (Shell Oil Co.)
E (lb/in2) 5409 CBR0.711 (U.S. Army Waterway Experiment Station)
E (lb/in2) 2550 CBR0.64 (Transport and Road Research Laboratory, England)
(See “Pavement Deflection Analysis,” FHWA Report HI-94-021, NHI, February
1994.) More detailed equations have been developed by correlating laboratory results
with fundamental soil properties. R. F. Carmichael III and E. Stuart (“Predicting
Resilient Modulus: A Study to Determine the Mechanical Properties of Subgrade
Soils,” Transportation Research Record 1043, Transportation Research Board,
National Research Council, Wa