Study On The Computer Tomography And Generalized Inversion Of Civil Engineering

Several new theory, key technica and practical methods of computer tomography and generalized inversion on civil engineering have been studied comprehensively and systemically to solve the current bootleneck problems existed in computer tomography on the basis of a synthetically review of its research history and state-of-the-art. A software of computer tomography system is developed. Moreover, Numerical simulations, indoor experimentations and practical examples are adopted to elaborate the scientificity. feasibility and application effectiveness of the research result, which also provide some scientific foundations of safety assessment, health monitoring and damage diagnosis for structres in civil engineering.The main contents and the conclusions of the study are described as follows:(1) The framework and methodology of computer tomography basised on generalized inversion is put forward. The framework include outdoor test and assessment, pre-processing, forward modelling and generalized inversion, result analysis and evaluation.(2) Discrete ill-posed problems confronted by computer tomography is studied. By the means of singular spectrum and picard plot, the essence of the difficulty to solve discrete ill-posed problems is analyzed.(3) The SIRT method is improved in this paper. The heart of regularization method is the optimum compromise between the solution norm and the corresponding residual norm, which is very meaningful to the other generalized inversion methods.(4) A series of generalized inversion methods and solution assessment index based on generalized inverse of matrix are proposed. The multi-object optimum method of evaluation function is adopted to sloved such an optimum problem and confirm the damp coefficient. The optimum methodology is not sensitive to initial value, and can always achieve a sensible solution.(5) The perturbation of three kinds of noise on the inversion solution is studied and wavelet analysis is introduced to reduce the noise. Backward error and backwardperturbation analysis is also discussed to analyze the computational stability of generalized inversion. Moreover, a practical method to take into account the transcendental information is put forward. And. it is also showed that generalized inversion methods have a better identifying precision under the same situation.(6) Several quantitive methods are propsed for identifying the velocity abnormity in tomography. The indoor test shows these flaw evaluation methods are more intuitionistic and exact than the other NDT methods.(7) The two dimension electrical resistivity tomography (ERT) uses the finite element method to carry out the forward model. The inversion routine used by the program is based on the smoothness-constrained least-squares method. Root mean squared error is the object function in the optimum problem .(8) Miller soil box is ameliorated and adopted to perform a standardized laboratory procedure for measuring soil electrical resistivity. Through orthogonal test, it is discovered that the influences of electrical resistivity are decreased in such an order: water content, pore-water electrical conductivity, degree of saturation, kind of soil. Then, an electrical resistivity model and its Archie's parameters of typical clay are established. Finally, A practical demonstration is given to illustrate the ability to find potential object by ERT. Combined with the electrical resistivity model. ERT will redound to forecast the water content of the soil.