Theoretical versus Measured Flexible Pavement Responses Under Dynamic Loading

Abstract

As mechanistic-empirical design of pavement structures advances toward full implementation, there is a need to evaluate the accuracy of theoretical load response models and backcalculation procedures employed in the design and analysis processes. To that end, a full-scale pavement structural study is underway at the National Center for Asphalt Technology (NCAT) Test Track to investigate the accuracy of the applicable models. Falling weight deflectometer (FWD) testing was conducted on eight different cross sections at the facility. The sections represented different pavement thicknesses, and use of modified and unmodified asphalt binders. FWD loads were dropped directly on top of and in close proximity to strain gauges and pressure cells embedded at different depths within the sections. This enabled the measurement of both surface deflections and in situ pavement responses under FWD loading. The surface deflections were used to backcalculate elastic layer properties within each test section. The properties were then used in forward calculation to compute stresses and strains at locations coinciding with embedded instrumentation. Direct comparisons were made between predicted pavement responses and measured responses to evaluate the effectiveness of both the backcalculation and forward calculation models. Better agreement was observed in the horizontal strain responses of the asphalt layer when compared to vertical pressures measured in the base and subgrade layers, respectively. However, it was generally found that layered elastic back- and forwardcalculation was sufficiently accurate for the conditions at the NCAT Test Track and also served to validate the sensor installation procedures.