Elastic waveform inversion in the frequency domain for an application in mechanized tunneling

The excavation process in mechanized tunneling can be improved by reconnaissance of the geology ahead. A nondestructive exploration can be achieved in means of seismic imaging. A full waveform inversion approach, which works in the frequency domain, is investigated for the application in tunneling. The approach tries to minimize the difference of seismic records from field observations and from a discretized ground model by changing the ground properties. The final ground model might be a representation of the geology. The used elastic wave modeling approach is described as well as the application of convolutional perfectly matched layers. The proposed inversion scheme uses the discrete adjoint gradient method, a multi-scale approach as well as the L-BFGS method. Numerical parameters are identified as well as a validation of the forward wave modeling approach is performed in advance to the inversion of every example. Two-dimensional blind tests with two different ground scenarios and with three different source and receiver station configurations are performed and analyzed, where only the seismic records, the source functions and the ambient ground properties are provided. Finally, an inversion for a three-dimensional tunnel model is performed and analyzed for three different source and receiver station configurations.

Automated summary

The excavation process in mechanized tunneling can be improved by reconnaissance of the geology ahead, which can be achieved through nondestructive exploration using seismic imaging. A full waveform inversion approach is investigated for tunneling, aiming to minimize the difference between seismic records and a discretized ground model. The inversion scheme incorporates various methods and is validated through numerical parameters and blind tests.