The Theoretical Study On Flow Rutting Of Asphalt Pavement

Rutting is the most popular distress in asphalt pavement of expressways. Along with the development of transportation systems, the production and growth of rutting have greatly changed. Concretely, the environment get warmer and load become more heavily; simultaneously much modified asphalt had been used in road construction. Then the flow rutting becomes the main form. At this process, the rutting ever mainly emerging in up and middle layers had changed to middle and bottom layers. The improvement of high temperature stability of middle layer causes to the failure of up layer. All the new conditions review that the pavement structure which get less concern has great impacts on the production of rutting. Surely studies on this part would influence the choosing of technology measures and have important practical significance to the developing phase of expressway which equally emphasizes construction and operation. The developing history of many subjects shows that the research on structure, which is one of the most important science issues in every subject, must refer to basic theory including strength theory and calculation methods and so on, and which can bring the further development of road engineering in the field of basic scientific research. Based on the above consideration, this paper carries on the theory research to flow rutting which mainly concerns the shape change under deviatoric stress.Based on the concepts of structure composition changing the spatial distribution of stress and strain and materials strength relating to stress state in three directions, this paper analyze the effects of structure using the solution of stress spatial distribution. Because the mechanical response emerges before the yield step of material and structure the theoretical analytical method of elastic layered system has been used based on quasi-viscoelastic parameters. Therefore, base on lofe solution of reaction force recursive method, do the modification of program and controlling of precision, make solutions to the mechanical response of layered system under multi-circularity vertical load and analyze the influencing laws of load quantities, load types and interlayer contacting conditions to complex stress state, and develop the calculation methods and program of present specification. Further present the atlas method of elastic layered system to show the stress spatial distribution of road struction; in order to realize the non-linear analysis, disperse the continuous system of physical and mechanical state into separate phases and make approximate analysis to structure evolution through the integration of every phase.Demonstrate the applicability and shortage of maximal shear strength theory based on the comparison of different shear strength theory. The key of study lies in the particularity of second principal stress. Through the application of generalized shear strength theory, this paper studies the dynamic change of elastic modulus and poisson's ratio in the evolvement process of pavement. And through combining with the displacement field observation of asphalt mixtures using non-contacting method, make approximate analysis to structure evolution of quasi-viscoelastic plastic system. The theory and calculation results show that the coupling effects among heavy traffic, warm environment and structure cause to the different contribution of every structure layer on rutting. The paper also proposes the condition of rutting emerging in middle and bottom layer in asphalt pavement with different base.Further the effects of structure composition on complex stress state and limit state of structure are also important. Based on this analyze the engineering measure through structure regulation to reduce the rutting. Besides propose detailed measures aim at the regulation of mechanical state between base and surface course and among asphalt surface course. At last combining with the study of strength theory using triaxial tests and considering the harmony among c andφ, E andμand viscosity and elasticity, discuss the basic law of asphalt mixture design based on the mechanical state control to layer position and present the concrete chart as reference of design. The theoretical analysis shows that the reasonable structural composition is valuable measure improving the performance of pavement and present basical condition. These conclusions conform to the practical experience in some test road under heavy traffic.