BENDING FATIGUE CHARACTERISTICS OF A REINFORCED MACADAM BASE

The traditional macadam base structure has poor resistance to road bending deformation. However, reinforcement methods to improve the performance of macadam base structures have not been fully explored. In particular, effective techniques to enhance the bending performance and fatigue life of flexible base structures are still lacking. In this study, geogrids were proposed to reinforce macadam base structures. Comprehensive tests were conducted to evaluate the bending performance and fatigue resistance of reinforced and unreinforced specimens. These tests included bending tensile strength tests, three-point bending fatigue tests, and cyclic loading tests applied at five distinct stress levels. The results show that unreinforced macadam bases have poor bending performance. When the load reaches the 0.8 stress level, the unreinforced specimens experience low-cycle fatigue failure, characterized by a small ultimate displacement and a distinct failure plane. With the inclusion of geogrid reinforcement, the fatigue life of the specimens is significantly improved, with no notable deterioration in the stress-strain yield curves even at high load levels. Reinforced specimens maintain high-cycle fatigue performance at the 0.8 stress level, thereby avoiding low-cycle fatigue failure. Furthermore, the reinforced specimens effectively suppress the propagation of mid-span reflective cracks in the cement-stabilized crushed stone base and delay the extension of diagonal shear cracks near the supports, thereby significantly improving the dynamic stability and long-term durability of the crushed stone base layer in the pavement structures. These findings provide a theoretical reference for the practical application of this reinforcement technology in macadam base structures. Keywords: highway engineering, reinforced macadam base, bending fatigue test, bending fatigue performance; geogrid