with iteration methods, unique solutions cannot be guaranteed and dif-

ferent sets of elastic moduli can produce results that are within the

specified (deflection or layer moduli) tolerance. In addition, elastic

layer programs generally assume an average (composite) modulus for the

subgrade layer without regard to the variation of the underlying soil

properties with depth. For sites with highly variable subgrade stiff-

nesses, it becomes very difficult to analytically match measured deflec-

tion basins using a composite modulus for the subgrade layer. There-

fore, there is a need to find a more viable way to determine the E-

values of pavement materials for a rational mechanistic analysis.

 Recent advances in in situ testing in geotechnical engineering have

 led to improvements in the determination of important soil parameters

 such as strength and deformation moduli. Unfortunately, the application

 of the improved techniques to evaluate or design pavements has been very

 limited. The Marchetti Dilatometer test (DMT) offers significant pro-

 mise for providing a reliable and economical method for obtaining in

 situ moduli of pavement layers, especially of the subgrade. There is

 also the potential of determining in situ moduli from the cone penetra-

 tion test (CPT) since several correlations between different deformation

 moduli and cone resistance have been reported in the geotechnical liter-

 ature. The CPT and DMT provide detail information on site stratifica-

 tion, identification, and classification of soil types which makes them

 attractive tests for the evaluation and design of pavements.


 1.2 Study Objectives

 The primary objective of this study is to develop procedures for

 the evaluation of material properties in layered pavement systems using