Development, Calibration, and Validation of Performance Prediction Models for the Texas M-E Flexible Pavement Design System

This study was intended to recommend future directions for the development of TxDOT’s Mechanistic-Empirical (TexME) design system. For stress predictions, a multi-layer linear elastic system was evaluated and its validity was verified by comparing the measured tensile strains under accelerated pavement (ALF) loading with the computed values. After reviewing all existing pavement performance models, the VESYS model was recommended for predicting flexible pavement layer rutting and an Overlay Tester-based fatigue cracking model was proposed, which includes both crack initiation and propagation models. For hot-mix asphalt (HMA) rutting predictions, the dynamic modulus test and repeated load test are proposed to provide material properties. The proposed HMA rutting model was calibrated using the rutting data from the NCAT test track and the Texas LTPP-SPS 5 test sections. The proposed fatigue cracking models were calibrated with performance data from NCAT. Resilient modulus and permanent deformation testing is recommended for base and subgrade materials and future research efforts are required to improve the repeatability of the permanent deformation test. For stabilized bases the traditional fatigue models are recommended and calibration factors were proposed based on existing accelerated pavement test data. A field experiment was conducted to evaluate the adequacy of the LoadGage program to compute allowable axle load limits for thin pavements. On sections trafficked to failure, very good results were obtained when moisture correction factors were applied to the laboratory measured engineering properties. Implementation should proceed by incorporating the proposed models and default material properties into a design software package, upgrading the available repeated load equipment, performing additional calibration, and developing additional default values for a wider range of Texas materials.