Evaluation of Subgrade Resilient Modulus for Pavement Design Using Mechanistic-Empirical Pavement Design Guide

This paper evaluates the effect of variation of the subgrade resilient moduli on the pavement design using the mechanistic-empirical pavement design guide (M-EPDG) analysis. Subgrade modulus values were obtained from three test sections on two routes in Kansas with an Intelligent Compaction (IC) roller and from the deflection tests using a Falling Weight Deflectometer (FWD). The deflection data was used to backcalculate the subgrade moduli using an elastic layer analysis backcalculation program and the Boussinesq’s equation. The pavement design analysis for various subgrade moduli was done with the M-EPDG version 1.0 software. The results show that the predicted total pavement deformation and roughness are sensitive to the subgrade modulus for flexible pavements. For Jointed Plain Concrete Pavements (JPCP), the key distresses are insensitive to the subgrade modulus. Asphalt base thickness has more influence on the total pavement deformation than the foundation layer. However, truck traffic plays an even more significant role in controlling this distress. The influence of subgrade modulus on the slab thickness in the JPCP design is insignificant. The “target” subgrade modulus for intelligent compaction control can be derived well before construction based on the soil type and asphalt base thickness and using the M-EPDG analysis. Achievement of this modulus in the field will lead to a reliable pavement structure for a given design period.