Study On The Dynamical Response Of Pavement Under The Random Loads

As automobiles develop in the way of large-scale and heavy-load, the over-load and over-limit phenomenon has become common than before and therefore the costs in the road maintenance have been increasing. So it is imperative to discuss the pavement respond under random moving load and it is also important in guiding significance and theoretical value for predicting the early destruction of pavement structures.Since there were some researches about the pavement structures under moving load ignoring the essential characteristics of loads and they were unreasonable especially for the over-load and high speed, the dissertation has adopted the random road as the input form of load, calculated the dynamic tire force by integral and discussed the influence factors, such as road grade, vehicle quality, vehicle parameters and driving speed.Based on the stratified elastic theory, the dissertation established three-dimensional finite element model of road, assumed that the tire track was rectangular and loaded in dual-axis and completed the dynamic response study of the interaction between vehicles and road surface in ANSYS successfully. The results of simulation showed that under the three-dimensional imposed load, the destruction of asphalt layer was caused by a large number of shear stress between different layers; the base and the subbase courses were the main layers bearing load, and the maximum horizontal tensile stress and the maximum transverse tensile stress all existed in the subbase course. So the destruction caused by tensile stress started from the subbase course, extended upward gradually and finally lead to the structural damage of the pavement.Since the main reason of pavement damage was caused by vehicle load, the pavement surfaces suffered the action of vehicle load and surrounding environment and the stress and strain in the road structure would lead to persistent or fatigue damage of the road. According to this situation, the dissertation also discussed the impacts of driving speed and road surface materials on the dynamic response of pavement. The results showed that the impact of speed on the dynamic response was in fluctuation and suggested to make a reasonable choice in order to avoid the peak value of dynamic response. It should be weighted that the requirements of reducing the fatigue damage and improving the comfortability and choose reasonable subgrade and surface modulus. The dissertation also proved that there was little effect for dynamic response of pavement when using different materials of soil base.In this dissertation, it made the fatigue damage of specific point as evaluation index and conducted road fatigue and fracture analysis. After applying the calculations of dynamic response, it can obtain the number of strain cycle for designated level of road when the road surface fatigue damage occurred.