Pile Integrity Testing Based On Wavelet Analysis

With the extensive application of the pile foundation, problems brought by the quality of pile are becoming more and more prevalent. The pile is abroad applied in various engineering field as common used foundation format and make certain social and economic benefits. It is very important to carry on pile quality testing in order to promise it's safe and dependable because it belongs to concealment engineering. The low-strain reflected wave method is abroad applied in foundation pile integrity testing in advance of low expenses, convenient fast and simple operates etc. But because the identification of detection wave mainly depend on the tester's experience, the traditional pile detection method often make errors, there are many aspects still need to be perfected such as its principle, experiment technique, especially in post processing and analyzing means.The wavelets theory combines together with applied sciences as theory sciences, is abroad applied in signal handling, mode identify, space investigate etc as a kind of technique tool and method. Wavelet analytical method has been developed during past several years as a new time-frequency analysis method. Wavelet analytical overcome the defect of short time Fourier transform, it has characteristic of multi resolution ratio, and has be applied to the field of frequency and time analyzing extensively.Firstly, the present paper overviews basic principle of low-strain reflected wave method, expounds testing technology of low-strain reflected wave method and testing gist of pile integrity, Discusses limitation and scope of application of low-strain reflected wave method and issue of testing blind area, analyses testing signal and identify foundation pile integrity combining engineering, and points out limitation and scope of application of low-strain reflected wave method.Secondly, in the foundation of sufficiently presentation wavelet theory, the present paper analyses Fourier transform and short time Fourier transform, discuss time-frequency localization properties of wavelet transform, expound multi-resolution analysis, wavelet decomposition theory and decomposing and reconstruction algorithm of wavelet decomposition, overview choice of the better wavelets series problem.At last, according to the characters of wavelet, the present paper, the db6 as a biorthogonal wavelets series is chosen. By MATLAB software and RS-pile testing system, wavelets is used to erase noise of foundation pile signal, confirm location of foundation pile shallow defect, remove baseline drift, and analyses signal by multi-resolution analysis. By comparison with traditional signal analysis measure of low-strain reflected wave method, result expresses that these analysis contributes to correctly identify the foundation pile integrity.