Montana’s Automated Deflection Analysis Procedure

Abstract

Economic conditions in the state of Montana during the past few years have dictated that the time and cost required to collect and analyze deflection data be significantly reduced. Consequently, the Montana Department of Transportation (MDT) undertook the development of an automated deflection analysis procedure (ADAP). This effort resulted in a PC-based Microsoft Windows application that provides a single program to assist the user in each step of the backcalculation analyses, from raw data to generated reports. The ADAP system consists of three components: preprocessor, main processor, and postprocessor. The preprocessor is used to import, validate, and extract deflection data and other pertinent pavement information from the Road Rater and MDT Oracle data base files and to generate the input for the MODULUS backcalculation program. The MODULUS program, which is the main system processor, is used to backcalculate in situ pavement layer moduli. The postprocessor provides the ability to generate reports and retrieve the analysis results, calculate the structural capacity and remaining life of the pavements in question, and upload the results to the MDT Oracle data base. In addition to providing for a more consistent, productive, and straightforward backcalculation process, the time and resources to perform the analysis of deflection data have been significantly reduced. Initial estimates indicate that instead of the 3 to 4 hr of work that were required for every hour of data collection, only 1 hr is now required, and this time will likely decrease as the MDT staff becomes more familiar with the program.