Experimental Study On The Impact Fatigue Performance Of Asphalt Mixture

Asphalt concrete pavement is widely used in its good road performance. At present,the high temperature stability of asphalt mixture, the low temperature crack resistance,water stability and so on are mature and effective, and can be used to study or test the evaluation equipment and methods of production. However, the fatigue performance of asphalt mixture, although there are MTS, UTM and other test equipment, but these testing equipment is expensive, testing complex, time-consuming and laborious. So the fatigue performance of the asphalt mixture is often limited in the research activity of the University, Institute, etc. At the same time, the driving load of pavement structure has impact characteristic,However, the fatigue properties of asphalt mixture are seldom analyzed from the angle of impact load.Based on the above situation, the paper studies the impact fatigue test equipment,test method and fatigue property of asphalt mixture. The main research contents and conclusions are as follows:First, analysis of mechanical response of asphalt concrete pavement under impact load.①Using ANSYS three-dimensional finite element numerical analysis platform, the numerical model of an asphalt concrete pavement under the load of moving vehicles is established, the moving vehicle loads on pavement mechanics response were analyzed.Research shows that under the moving vehicle loads(speed), the road pavement structure table calculation of vertical stress in 0.1s time rapid increase to 0.898 MPa,then quickly within 0.1s time decreased rapidly to 0mpa. And with the increase of depth,the trend is fast, and when the top of the road table is 5.97%, when the soil base has been reduced to 0.75% of the road table, the vertical stress change of pavement structure caused by vehicle load is in accordance with the law of impact.②The vehicle moving loads are simplified to vertical or vertical and horizontal loads. The mechanical response of pavement structures in different simplified modes is analyzed respectively. The results show that the moving load has little effect on the vertical stress and the vertical displacement of pavement structure. The moving load of the vehicle level mainly affects the response of pavement structure to the process. Based on the above conclusions, the moving load of the vehicle is simplified as a moving constant vertical load.③The impact load model of the Marshall automatic hammer is established, and the action law of the Marshall auto- impact load on asphalt mixture is analyzed. The mechanical response of pavement under the action of vehicle moving load and impact load is compared, and the law of the two is found. Therefore, the load of the vehicle is replaced by the impact load of Marshall automatic hammer.Second, development of impact fatigue test machine, and the asphalt mixture samples for high-temperature stability, water stability and impact fatigue, and other comprehensive road performance test analysis.①Drop hammer impact fatigue testing machine for reference and SHPB impact pressure bar device, according to the results of the first part of the numerical analysis, of Marshall automatic hammer meter for refit, made of impact fatigue testing machine.②The parameters of the impact fatigue test and the test method were determined by the experimental study on the loading mode and strain rate of the impact fatigue test machine.③The asphalt mixture samples prepared, and the comprehensive road test of asphalt mixture were carried out. Experiments show that corresponds to the asphalt mixed material maximum fatigue life exists an optimum asphalt content and the optimum asphalt content than the specification specified with larger than the design to determine the optimum asphalt content. The fatigue life of asphalt mixture is shortened with the increase of the maximum nominal particle size of asphalt mixture. For the same maximum nominal particle size, the asphalt mixture with different thickness, the thinner the gradation, the longer fatigue life. At the same time, the fatigue life of asphalt mixture with different gradation is bigger, and the SMA-13 is more than AC-13 and OGFC-13.