A Study On Guided Wave Theory Of Hollow Circular Cylinders And Plate-like Concrete Structures

The quality of hollow circular cylinders,such as metal tubes and pipe piles,and plate-like concrete structures,such as concrete plates,road surface and diaphragm walls, determine the safety of their operation.The conventional non-destructive detection method of metal tubes is the ultrasonic method.However,there is a great difficulty in long-range inspection with the conventional ultrasonic method,because this method is a single-point detection means.The traditional non-destructive method of pipe piles and concrete plates is impact-echo technique based on one-dimensional stress wave theory, and it can detect the big defects.It is feasible to solve the problems such as the big area general detection of metal tubes and the small defects detection of concrete structures by using of the non-desructive method based on three dimensional guided wave theory.By means of theoretical analysis and experimental study,combing with numerical simulation method,some problems of non-destructive testing technology of metal tubes, pipe piles and concrete plates are researched based on guided wave theory.The reseaches mainly focus on the following aspects.(1) The frequency equations in metal tubes are solved by Matlab program.The guided wave dispersion relations provide information about group velocity and phase velocity as a function of frequency.The dispersion curves and displacement curves are drawn by solving the frequency equations.The characteristic of dispersion curves and displacement curves in different guided wave modes are detailedly analyzed.There are some guides on how to choice guided wave modes and how to choice the excitation frequency to detect the metal tubes.(2) The guided wave inspection instrument is produced by designing the guided wave detection system.The experimental research and experimental tests are executed in the model tubes.It is a theory base of the practical application of guided wave detection system.(3) The conventional NDT of pipe pile is the impact-echo method based on one dimentional stress wave theory.The possible problems of pipe pile testing by using of one dimentional wave theory are analyzed contrasting the on-site experiment.There is a detailed analysis of pipe pile based on three dimentional guided wave.(4) The frequency equation in a traction-free pipe pile is solved.Parametric analyses of pipe pile's diameter,the thickness of pipe pile,wave speed and Posson's ratio to dispersion relation are discussed in detail.There is a contrast of hollow pipe pile and solid prime pile.(5) The dispersion equation of pipe pile embedded in soil is detailedly derivated. The effect of the conventional pile dynamic testing technology influenced by guided wave theory is analyzed.(6) It is the common method of the impact-echo technology using in concrete plate detection.The possible exiting problems of the traditional impact-echo method using in concrete plate are analyzed.The new non-destructive testing technology based on Lamb wave is put forward.(7) The dispersion equations of the concrete plate are derivated in different condition,including the traction-free,free-fixed condition and embedded in soil in both side.The dispersion equations are solved by the Maple program.(8) Results of parametric analyses show that the dispersion curves are not affected by boundary conditions.The attenuation curves are affected by the boundary conditions. The influence of the soil action to concrete plate testing is discussed by analyzing the real part and the imaginary part of wave number.(9) The influence to dispersion curves of concrete-to-soil shear modulus ratio and concrete-to-soil density ratio.Parametric analyses of plate thickness,Poisson's ratio and soil type are discussed.(10) Why there are multi-peak in frequency spectrum are explained by analyzing the propagation mode of guided wave combing with impact-echo example.It is a guide to conventional impact-echo method by studying guided wave.