Equivalent Granular Base Moduli: Prediction

A simple, but accurate, technique to determine the equivalent one layer modulus for unbound aggregate material in a flexible highway pavement that accounts for the nonlinear behavior of the granular material has been developed. The solution is based upon predictive regression equations developed from an analysis of multi-layer elastic theory computer solutions. The equivalent granular moduli is a function of all pavement layer parameters influencing the bulk stress in the granular layer (surface and base thicknesses; surface and subgrade modulus and base course quality related to the K₁ value in the nonlinear modulus expression: M_R = K₁-4830^0.5. Nomographic solutions are also presented. Comparison of this method shows relatively good agreement to methods developed by the U.S. Army Corps of Engineers, Kentucky Highway, and Shell Oil. Since the procedure accounts for significant factors affecting the nonlinear response of unbound granular materials, the technique is recommended for use in highway pavement design and analysis using theorectical layered approaches.