Study On Pavement Surface Function Accelerated Loading System

With the continuous development of our country's preventive maintenance technology, kinds of pavement treatment measures are widely applied. Foreign ready-made pavement treatment measures do not fit the actual situation in China, because the cycle of system study of carrying out highway maintenance and preventive maintenance is too short, and related processes and technologies are still at the initial stage of learning, introducing and imitating. In the meanwhile, domestic and international road sector emphases on bearing capacity of pavement structure in past years, but functional damage to the road and the resulting impact on the structural damage are paid insufficient attention to. In addition, it is lack of the necessary experience and reserves data and related research methods. The outstandiang problem is that there are always not appropriate and effective pavement surface functional evaluation methods. The indicators, raised by contractors from the standpoint of commercial profits, are so lack of scientificity that they are not suitable for actual projects and for construction and quality assessment, which induces that many inherent problems such as skid resistance decline after fog seal, noise deduction of chip seal and so on have never been figured all out. Therefore it is necessary to improve and optimize existing pavement preventive maintenance measures and to better the application of maintenance materials on surface treatment and to improve the development of preventive maintenance.The purpose of this study is to optimize evaluation system of pavement performance evaluation system, determine pavement performance attenuation laws and optimize construction technology, laying the foundation for quantitatively evaluating pavement surface treatment modes and developing new skills and technologies. The main work and innovation are concluded as follows:The feature and mechanism of current accelerated loading test machines in china and abroad are analyzed, and a new type of main-drive-wheel pavement surface material accelerated loading test system is designed and exploited according to mechanical principles, as well as the test molds, which will be mainly applied on evaluation research of pavement surface functions. Then geometric calculation is carried out, which indicates that the traditional arc press plate doesn't match with the exploiting test models, while a straight plate is appropriate.The friction effect mechanism between the tire and pavement is analyzed under different working conditions, which concludes that the initiative drive-wheel model is most suitable to the accelerated loading test. In addition, by analyzing the complete stress situation when the car is moving, it is indicated that the cycle type accelerated loading models such as circular track test is not very consistent with practical situation. The simulation test can be done only when the tire ran direction is coincidence with the direction of the pavement center line.Based on the new accelerated loading system, corresponding test methods and regulations are prescribed and experimental conditions and parameters are determined to ensure the stability and reliability of test results. Two functions pavement friction and noise are tested and evaluated. It is found that load affects pavement friction coefficient most, followed by tire pressure and speed, but the influence of temperature is feeblish. In addition, the friction coefficient of moist pavement is always lower than that of dry pavement, so it is more dangerous to travel in rain days. The result of noise test shows that speed greatly influences tire/pavement noise, and the correlation coefficient of the regression equation reaches 0.913. According to the frequency spectrogram, the peak value of tire/pavement noise lies in the spectrum 800Hz~1000Hz.Based on the idea of reverse engineering, the concept of pavement converse design is proposed, and old asphalt pavements are remodeled. The results show that remodeling pavement has high similarity to the original pavement, and the similarity gets better with the time of accelerated and loading test. The entropy of pavement skid resistance raises after surface treatment, indicating that pavement maintenance tends to unify each subsystem and make the function of the whole structure more stable.According to fog seal treatment research by accelerated loading test, important achievements are scored as follows:(1) The attenuation of pavement performance under'Do-Nothing'conditions is reviewed, and the indicators are found to be consistent with'S-type'function characteristics. And equation are fitted with correlation coefficients higher than 0.9.(2) Four different dosages of asphalt materials are used on remold pavement, the jump rate of pavement performance is calculated by comparing test results with untreated pavement, concluding that the best dosage is 0.5kg/m2. In the meanwhile, performance of pavement post-treated with sand spray is better than brushing asphalt only, and the average performance jump rate increased by 50%.(3) After fog sealing, sanding process can increase the pavement anti-slide performance. Sanding process and mechanism are discussed, and factors, such as sand particle size, spreading volume, quality, angularity which could affect pavement performance, are focused on. Ii is concluded that sand with 1.18mm particle size is the best choice, and the suitable dosage is about0.5kg/m2. Diabase and basalt are good for spraying considering the durability, surface vision and price. It is also found that natural sand with smooth surface is weak in bonding with the asphalt, leading to negative results, for example roll ball effect. Besides, it may even cause negative effects, which will get more serious with larger particles. Therefore, natural sand is not recommended to be used for post-processing of fog sealing.