Propagation Characteristics Of Elastic Wave In Inhomogeneous Layered Media And Its Application In Geotechnical Engineering Detection

It is an important subject to investigate the internal structure in themedia using various kinds of detection methods in geotechnicalengineering. Especially to detect the defect in the underground structuressuch as tunnels, there is much limitation in the existing detection methods.In order to clarify the propagation characteristics of elastic wave ininhomogeneous layered media, a series of FEM dynamic analysis arecarried out based on the propagation theory of elastic wave in layeredmedia. The parameters including S-wave velocity, density, thickness andimpedance ratio affect on the waveform properties, spectrumcharacteristics and time-frequency characteristics of elastic wave arediscussed. And it is paid special attention on the structure with lowvelocity interlayer; the propagation characteristics of elastic wave andsensitivity of parameters are evaluated. Then the relationship between theimpedance ratio and the waveform properties, spectrum characteristics andtime-frequency characteristics of elastic wave are obtained.Tianjin Haihe immersed tube tunnel grouting constructionsuccessfully used elastic wave imaging method to real time monitor anddetect grouting effect. In this paper the data acquisition system, analysismethod and visualization method are detailed introduced. The groutingeffect can be real-time monitored and evaluated by visualizing thewaveform, spectrum and time-frequency characteristics of elastic wave.Comprehensive evaluation standard can be established by normalizing andcomparing of the elastic wave before and after grouting based on the relationship between impedance ratio and waveform, spectrum andtime-frequency characteristics of elastic wave. Based on thecomprehensive standard, the whole immersed tube tunnel grouting effectcan be qualitatively evaluated.