Study on Waveform Inversion Method for Elastic Parameters of Stratified Medium and Its Applications

The waveform inversion method was used to reveal the physical and mechanical properties of underground medium, which comprehensively utilized the amplitude, travel time and phase of wave field. A typical stratified medium model in geotechnical engineering investigation was established for grasping the intermediate medium properties. In forward calculation, response waveforms were achieved by the finite-difference time domain (FDTD) method; and, in inversion analysis, the least squares method was adopted. From the response waveforms, it is found that the higher the P-wave velocity of the intermediate layer is, the smaller the amplitude of response waveform is; while the thicker the intermediate layer is, the more waveform phase is deferred. The feasibility and accuracy of the waveform inversion method was verified. Furthermore, this method was used in the detection of grouting quality of immersed tube tunnel. Based on the waveform data collected on site, the P-wave velocity and thickness of the grouting layer were revealed by inverse calculation and the grouting quality was effectively evaluated.