Development Of A Flexible Pavement Design Procedure Based On The Mechanistic - Empirical Pavement Design Guide: A Case Study
Abdullah, Ali Qays
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This research developed design tables of new flexible pavement structures for New York State Department of Transportation based on the Mechanistic Empirical Design Guide (MEPDG). The design tables were developed using the MEPDG software for Regions 1, 3, and 7 for Upstate part of New York State and for Regions 8, 10, and 11 for the Downstate part of New York State. The MEPDG software was used to run design cases for combinations of: climate conditions, traffic volume, subgrade soil stiffness (Mr) and pavement structures. The conditions that the MEPDG was used to run were: the road structures classified as Principal Arterial Interstate, design 95%reliability level, 15 and 20 year analysis period. Weight in Motion (WIM) data of Region 7 were used for Region 1 and 2, also WIM data of Region 8 were used for Region 10 and 11. Climatic data specifically for each region were used. The NYSDOT's Comprehensive Pavement Design Manual (CPDM) was initially used to obtain pavement design solutions for Region 7 and 8. The granular subbase materials and thicknesses recommended by CPDM were used but only the asphalt layer thicknesses was varied to include several values higher and lower than the thickness recommended by CPDM. The thickness of asphalt binder and surface layers were kept constant. Only the thickness of the base layer was changed.For each design combination, the design case with thinnest asphalt layer for which the predicted distress was less the performance criteria was selected as the design solution. The design solutions for Regions 7 and 8 were assembled in design tables. The examination of the design tables proved that, in general, Region 7 requires thicker pavement structures than Region 8 for same Annual Average Daily Truck Traffic (AADTT) and Resilient Modulus.In the second phase, the MEPDG was used to run for Region 1, 3, 10, 11. The design solutions were tabulated first to produce the design tables for each design case. Since it was expected that the climate changing has no effects on the design solutions for the regions which belong to the same New York State part, the design tables of Region 7 were compared with the design tables of Regions 1 and 3. In addition, the design tables of Region 8 were compared with those obtained for Regions 10 and 11. The comparisons proved that the change in location within the same part of New York State affects the design solution for the same combination of subgrade soil stiffness and truck traffic volume. In the third phase, the design tables for 80% design reliability were produced for each selected region. The design tables which were developed by this study provide flexibility to the designer to design the new flexible pavement structure. The designer should select the subgrade (Mr), AADTT, design life, and the design reliability; then, the design solution could be obtained directly from the tables.