Analysis Of Asphalt Pavement Structural Performance Based On The Semi-rigid Base Cracking

Because of it’s high strength, low cost, integrated and it’s water stability, semi-rigid asphalt pavement has been widely used in China’s highway construction. However, there is some micro-cracks in semi-rigid base when they were constructed. The micro-cracks can be easily expanded into a base cracks run through the entire thickness by traffic load and temperature load of redundant role, and expanded into the bituminous layer to form reflective crack possibly. The cracks would weaken the structure and reduce the impact of pavement life.The paper investigated the semi-rigid base cracking situation and analyzed cracking mechanism and classified the cracks, and made a concept of Base Cracking Degree. Use Fracture mechanics and finite element method to analysis the semi-rigid base cracks forming and the fatigue cracks extending life, as well as mechanical analysis of semi-rigid base of different Base Cracking Degree and analyzed the modulus decay law. Finally, the semi-rigid structure design methods based on Cracking Degree. The Result indicated that:The deflection of semi-rigid base completely cracking (a crack) is little increase than those without cracks; There is a considerable stress mutation value level in base cracking tip than the base without cracks; The base is not easy to crack and the crack propagation with Thicker primary and high modulus; The crack propagation was divided into two stages, the rapid expansion phase and slow expansion phase; Increasing the base modulus and the thickness can boost base structure fatigue life, however the modulus increases to 5000MPa above, the fatigue life of the growing trend would be stability; The value of Cracking Degree base with different thickness greater, the deflection would be larger, but the greater thickness, the deflection of base with the same value of Cracking Degree would be smaller; The value of Cracking Degree base with different thickness greater, the stress in asphalt layer bottom would be greater, but the greater thickness, the stress of base with the same value of Cracking Degree would be smaller; The equivalent elastic modulus calculated according to deflection equivalent, as base Cracking Degree decreased, and little impacted with base thickness; The base modulus decay law explained that the macro-cracks will cause a reduction of the "active" cross sectional area, for uniaxial tensile stress, which reduced the bearing capacity of entire structure of the pavement.