Research On Dynamic And Fatigue Analysis Of The Base Layer Of Asphalt Concrete Pavements

The economy of china is on the stage of fast developing, and the arteria of economy is transportation, of which the most important part is highway transportation. In view of that, the quality and durability of highway are more and more attached importance to. And the performance of highway depends on the base layer of the road. According to the domestic and overseas experiences, asphalt concrete soft base layer is more durable than the traditional cement concrete semi-rigid base layer and has better performance. But the research about semi-rigid base layer is far maturer than that about asphalt concrete soft base layer. With the spreading domestic usages of soft base layer, the research about it becomes more and more important and urgent.In the traditional research and gauging of the road surface and base, the resistance transducer, whose defects are easy-broken, unstable and sensetiveless, is the most used transducer. The vibrating wire transducer, which is seldom used in domestic road research, overcomes the defects of the resistance transducer. The using of the vibrating wire transducer in a repair project of a domestic national highway is a meaningful try.This dissertation associates with a repair project of a domestic national highway. Basing on the datum gotten in-situ from transducer, soft base layer structural modal of the road is established in the finite element software, and dynamic analysis is carried out. Using the rules of fatigue of asphalt concrete concluded by former researchers, fatigue life can be estimated and referable analytical results can be achieved.The specific tasks done in this dissertation are as follow:1. Using vibrating wire transducer and resistance transducer to get the in-situ datum of deflection and strain;2. Establishing the road structural modal in general finite element software ANSYS, comparing the in-situ gauged deflection and strain with the results of ANSYS static analysis to confirm the modal's boundary conditions, making the modal more compatible with the real situation.3. Using ANSYS to carry out road dynamic analysis, simulating a vehicle with 10-ton weighted rear axis running through the cement concrete surface board in 70km/h, and obtaining mechanical response datum from this;4. Doing statistic about the cracks on the cement concrete surface boards, spotting out the endpoints and five-divided points of a crack, confirming the fatigue controlling points through the discrete-point column graphs;5. Getting the time-history curves of the fatigue controlling points from ANSYS, adopting the Miner lineal accumulating- damage theory and rain-stream counting method to calculate the fatigue life of the controlling points in the base layer.The fatigue life calculated in this dissertation is the result in the ideal situation. For the reason that many practical factors are not able to be considered, the result has a gap to the real fatigue life. But, when more infecting factors are added to the finite element modal in this dissertation, a better analytical result must be achieved. In view of this, the investigation in this dissertation has made a firm foundation for gaining the practical result in the future.