APPLICATION OF DEFLECTION TESTING TO OVERLAY DESIGN: A CASE STUDY

In the fall of 1985, the Engineering Research and Development Bureau (ERDB) of the New York State Department of Transportation (NYSDOT) and the Cornell University Local Roads Program undertook a case study involving the application of the falling weight deflectometer (FWD) to pavement evaluation and overlay design. The site for the case study was a 1-mi section of state highway in the Finger Lakes Region of Central New York State, which had already been scheduled to receive an overlay during the 1986 construction season. Nondestructive pavement testing was conducted in December 1985 and May 1986. Pavement layer moduli were back-calculated from the FWD data using the computer program MODCOMP 2. As a part of the study, a mechanistically based computer program, called PAVMAN, was developed to calculate remaining pavement life and required overlay thickness. The pavement layer moduli determined using MODCOMP 2 were used with the PAVMAN program to estimate the remaining life of the existing pavement and determine the required overlay thickness. The results obtained with PAVMAN compared well with design overlay thicknesses determined using more traditional methods of overlay design (such as engineering judgement and the Asphalt Institute's deflection based method).