An Evaluation of In-situ Elastic Moduli from Surface Deflection Basins of Multilayer Flexible Pavements: A Study of Flexible Pavement Base Courses and Overlay Designs, Second Cycle of Research at the Pennsylvania Research Facility

摘要

Determination of in-situ modulus is an essential step in the nondestructive structural evaluation of flexible pavements. The research herein was undertaken to develop a method for evaluating the in-situ modulus of each pavement constituent layer by using surface deflection basins. The elastic layer theory and the Gaussian method of elimination were used to formulate surface deflection in terms of elastic modulus, load intensity, and layer thickness. The resulting equations were very complex, so that it was impossible to compute layer modulus directly from surface deflection basins. These equations, however, were used to analyze the effect of changing layer modulus on the surface deflection. On the basis of this analysis, a computer program for calculating in-situ modulus values from Road Rater deflection basins was developed, essentially by incorporating iteration procedures into the BISAR computer program. Using the developed computer program, the in-situ modulus of each pavement constituent layer of some of the experimental pavements at the Pennsylvania Transportation Research Facility was computed. The effect of various influencing factors on the in-situ moduli was investigated.