Application of graphical method in analyzing falling weight deflectometer (FWD) data

Abstract

Deflection measurements have long been used to evaluate the structural capacity of in-situ flexible pavements. The structural evaluation of flexible pavements is recently carried out mostly with the Falling Weight Deflectometer (FWD) in the state of Texas. Texas Department of Transportation (TXDOT) District Pavement Engineers have used the Texas Transportation institute's MODULUS 5.0 layered elastic program to evaluate in-situ pavement performance by determining layer moduli for flexible pavement. This program is very useful and reliable especially when the pavement layer information is available. Currently, many TXDOT District Pavement Engineers are interested in a more direct method in analyzing the FWD deflection data. This thesis presents a direct method of analyzing the FWD deflection data using deflection basin parameters, maximum deflection and appealability. The direct method proposed herein can be suited for the Department Engineers (a) to rapidly analyze thousands of FWD data in a network level project having insufficient or doubtful pavement layer information and (b) to graphically analyze project level deflection data on a spreadsheet before running the Modulus program. For the analysis, FWD deflection measurements and layer information from the Long Term Pavement Performance (LTPP) database were utilized. The proposed direct method using deflection basin parameters might be very promising as a simple, graphical method to evaluate the strength of pavements prior to running Modulus 5.0 program and to identify pavement performance.