EFFECT OF GEOGRID REINFORCEMENT ON FLEXIBLE PAVEMENT PERFORMANCE OVER WEAK SUBGRADE UNDER DIFFERENT LOAD CONDITIONS

Abstract

Flexible pavement constructed over a weak subgrade is subject to premature failure, such as severe rutting, cracking, and a high level of tensile strain at the bottom of the asphalt layer, which affects pavement service life. To overcome such issues, geogrid material is used to reinforce pavement layers. Most laboratory studies are limited to single load or static load conditions that provide insufficient explanation for pavement response under repeated dynamic loads. In this study, the responses of flexible pavement reinforced with biaxial and triaxial geogrid were evaluated using a laboratory 1/3 scale accelerated testing device at three loading scenarios (5, 6.5, and 7.5 KN). Five pavement sections were tested: control (unreinforced), triaxial and biaxial geogrid reinforcement at the middle of the subbase course layer, and at the subbase-subgrade interface. The surface rutting and tensile strain at the bottom of the asphalt layer were measured to evaluate the effect of reinforcement type and location. Results revealed that geogrid reinforcement, especially triaxial geogrid when placed at the subbase-subgrade interface, can significantly minimize rutting depth and tensile strain at the bottom of the asphalt layer. Triaxial geogrid at the interface reduced rutting by an average percent of 45%, tensile strain at the bottom of the asphalt layer by 84% relative to the control section, and a Traffic Benefit Ratio (TBR) of 4.0-4.3 corresponding to 303-326% improvement of load repetition.