Structural Improvements of Flexible Pavements Using Geosynthetics for Base Course Reinforcement

A study was conducted on full-scale pavement test sections to assess geogrid/base reinforcement in flexible pavements representative of major highways. The experimental design, trafficking protocol, results and development of rutting models are reported herein. Accelerated trafficking was conducted with a heavy vehicle simulator on eight pavement test sections. Four test sections were reinforced with geogrid placed at the base/subgrade interface, the other four were matching unreinforced (control) sections. Rut depths in the pavement surface as a function of applied traffic cycles were compared. Except for the thickest base and asphalt combination tested, the grid reinforcement provided benefit compared to unreinforced control sections as indicated by surface rut depth. (Four test sections reached ‘failure’ and four did not—traffic ceased at a set number of load cycles in these cases.) Empirical rutting models presented in NCHRP 1-37A, Guide for Mechanistic-Empirical Design of New and Rehabilitated Pavement Structures (available from http://www.trb.org/mepdg/) were extended to account for the reinforcement. Mechanistic finite element models were calibrated using strains measured throughout the test sections. Predicted rut depths using this mechanistic-empirical approach were in reasonable agreement with measured values. For the pavement configurations of this study, geogrid was predicted to increase the pavement life by 29 to 43%.