Determining Moduli of Materials from Deflections

In the reported investigation flexible pavement evaluation charts were developed as follows: (a)A subgrade evaluation chart which utilizes the maximum deflection and the spreadability data from the dynaflect tests, and is based on Terzaghi's equation; and (b)a subgrade evaluation chart and pavement evaluation charts based on the same thinking as that of Westergaard and Pickett. Ten sections of satellite projects were evaluated during their construction by taking deflection data on the subgrade and on each layer of the pavement. With these data and the charts, average values of the elastic modulus of the materials were estimated. The subgrade modulus varied from 4,000 psi to 8,000 psi (28 MN/m² to 55 MN/m²) depending upon the soil type; the cement treated subgrade modulus was 100,000 psi (690 MN/m²); that of the cement treated aggregate was 150,000 psi (1,035 MN/m²); that of the untreated aggregate sandwiched between asphaltic concrete and cement treated layer was 50,000 psi (345 MN/m²); and that of the asphaltic concrete was 100,000 psi to 1,000,000 psi (690 MN/m² to 6,890 MN/m²), depending upon the seasonal temperatures.