Dynamic Inverse-analysis Of Viscoelastic Multi-layered Soil

The research methods and engineering applications about the dynamic response of the multi-layered soil as well as the inverse-analysis of the soil structure both in domestic and abroad are discussed in this paper. Aimed at the identification problem of the material properties of the viscoelastic multi-layered soil under dynamical load, the problem of dynamic response of the viscoelastic multi-layered soil is studied systematically. Then, the system identification method is used to study the related dynamic inverse analysis. The major contents and research results are as follows:1 Considering the state-of-the-art of dynamic response of the viscoelastic multi-layered soil, the response of the symmetric problem of the viscoelastic multi-layered soil due to dynamical load is studied systematically. The expression of dynamic response is derived from the fundamental equation in the frequency domain. An analytical solution of the surface displacement of the problem is given. Further more, the numerical integration technique is investigated to solve the problem of the double oscillation of the integrated equations. The computational results are verified by using the previous survey data.2 Using the finite element method, the response of the symmetric problem of the viscoelastic multi-layered soil due to dynamical load is studied in time domain. The dynamic equation of the viscoelastic soil is derived and the Wilson - 6 method is used to solve the equation of Burgers model. The results are verified by comparing with the results in references. Numerical results show that the method is of high validity and precision. It can easily obtain a satisfactory result, especially for the short-time loads.3 By a FFT (Fast Fourier Transformation), the falling weight deflectometer (FWD) data, namely, the load pulse and displacement pulse of the tested curve, is transformed from the time domain to the frequency domain. Then, dynamic analysis is performed to obtain the characters of the tested soil. It is discussed and analyzed why usually, in the end of 60 millisecond sampling area, the data of the displacement is not zero. After discussed and analyzed, a new method is suggested to correct the truncation error. Then, a number of FWD data are analyzed.4 Using the system identification method, a displacement depended inverse analysis of the parameters of the viscoelastic multi-layered soil has been done in the timedomain and the frequency domain, respectively. The validity of the method is verified by several examples. Numerical result shows the method is of good stability and high accuracy, and reliable to identify the material properties.5 A two-parameter creep compliance formulation is utilized to characterize the viscoelastic behavior of the asphalt pavement surface layer. And the properties of the base and the subgrade adopted the complex damping theory. Based on the FWD data, the system identification method figures out the dynamic parameters of a real pavement structure. The computational parameters are reasonable to the engineering expectation. It shows that the dynamic analytical model here is suitable to the pavement structure and the method is of validity to the pavement identification problems.