| After twenty years' reform and opening, we make much progress in highway construction. With the development of transportation, people begin to know clearly that the influence of the highway to the national economy is very important. The investment in the highway projects is much more than ever in world, so scientific management has been impendent request and researching hotspot. In order to manage the pavement scientificly, firstly we must test and evaluate the pavement scientificly. Through the periodic testing and evaluating, we can judge it's possible condition in the future and provide necessary technology information for pavement management system and maintenance program.To test and evaluate the pavement scientificly, in the near twenty years, people attach increasingly importance for the study of pavement nondestructive test and material properties backanalysis. The study of pavement nondestructive test and material properties backanalysis will be beneficial to controlling highway construction quality, understanding the long-period use properties of pavement in depth, improving pavement design, optimizing highway reconstruction plan and improving highway maintenance. Some countries taped many kinds of new testing devices one after the other and built perfect testing and evaluating system. Deflection is the most popular target in pavement testing, it's test and analysis technology advances very quickly. Since inventing deflectometer in 1953, the pavement deflection testing instrument has developed from static deflectometer to falling weight deflectometer (FWD) and it has developed from the biggest deflection testing of the single point to the testing of pavement deflection basin. The technology of pavement moduli back-calculation is developed along with the appearing of falling weight deflectometer (FWD). The newest deflection testing instrument, such as FWD, has the characteristics of high speed, reliable, nondestructive and abundant information, so it makes it possible that we can back-calculate pavement layermoduli by use of measured deflections, we can ulteriorly analyze pavement structure's stress and strain conditions and evaluate the carrying capacity of pavement. Thereby, the technology of back-calculation of pavement moduli rapidly became the important matter of research and spread internationally, and some application software and programs are taped.At the same time, most of present backanalysis software with broad applications are based on the theory of axes symmetrically and multi-layered linear elastic hypotheses, such as Modulus, Modcomp, Wesde^ SIDMOD etc. These software's superiority is that they accord with the present design theory and the speed of back-calculation is very fast; but their bug is also very obvious, the nonlinear property is ignored and the errors are bound to produced. Especially when we back-calculate the properties of subgrade material, the back-calculation value of subgrade moduli will be larger than the actual value if we ignore it's nonlinear property. So when we back-calculate the material property of pavement, we must consider the nonlinear properties of material and adopt more actual pavement mechanical model. This is the inevitable development direction of pavement moduli back-calculation.To this question, in this paper, pavement layer linear elastic properties and subgrade nonlinear properties are studied systemically based on finite element method and system identification principle. The main research contents are as follows:1. Several nonlinear constitutive elastic models which are used to calculate pavement material nonlinear properties are described in detail and their merits and shortcomings are analyzed. Furthermore, different nonlinear constitutive models are chosen to simulate corresponding subgrade material when we back-calculate the nonlinear properties of subgrade material.2. A new road roller ?landpac impactive compaction machine is introduced systemicly. This kind of roller can acquire compaction effect in deep layer a... |
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